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  1Chapter 7 - Inside The View Layer
  2=================================
  3
  4The view is responsible for rendering the output correlated to a particular action. In symfony, the view consists of several parts, with each part designed to be easily modified by the person who usually works with it.
  5
  6* Web designers generally work on the templates (the presentation of the current action data) and on the layout (containing the code common to all pages). These are written in HTML with small embedded chunks of PHP, which are mostly calls to helpers.
  7* For reusability, developers usually package template code fragments into partials or components. They use slots to affect more than one zone of the layout. Web designers can work on these template fragments as well.
  8* Developers focus on the YAML view configuration file (setting the properties of the response and other interface elements) and on the response object. When dealing with variables in the templates, the risks of cross-site scripting must not be ignored, and a good comprehension of output escaping techniques is required to safely record user data.
  9
 10But whatever your role is, you will find useful tools to speed up the tedious job of presenting the results of the action. This chapter covers all of these tools.
 11
 12Templating
 13----------
 14
 15Listing 7-1 shows a typical symfony template. It contains some HTML code and some basic PHP code, usually calls to variables defined in the action (via `$this->name = 'foo';`) and helpers.
 16
 17Listing 7-1 - A Sample indexSuccess.php Template
 18
 19    [php]
 20    <h1>Welcome</h1>
 21    <p>Welcome back, <?php echo $name ?>!</p>
 22    <h2>What would you like to do?</h2>
 23    <ul>
 24      <li><?php echo link_to('Read the last articles', 'article/read') ?></li>
 25      <li><?php echo link_to('Start writing a new one', 'article/write') ?></li>
 26    </ul>
 27
 28As explained in Chapter 4, the alternative PHP syntax is preferable for templates to make them readable for non-PHP developers. You should keep PHP code to a minimum in templates, since these files are the ones used to design the GUI of the application, and are sometimes created and maintained by another team, specialized in presentation but not in application logic. Keeping the logic inside the action also makes it easier to have several templates for a single action, without any code duplication.
 29
 30### Helpers
 31
 32Helpers are PHP functions that return HTML code and can be used in templates. In Listing 7-1, the `link_to()` function is a helper. Sometimes, helpers are just time-savers, packaging code snippets frequently used in templates. For instance, you can easily imagine the function definition for this helper:
 33
 34    [php]
 35    <?php echo image_tag('photo.jpg') ?>
 36     => <img src="/images/photo.jpg" />
 37
 38It should look like Listing 7-2.
 39
 40Listing 7-2 - Sample Helper Definition
 41
 42    [php]
 43    function image_tag($source)
 44    {
 45      return '<img src="/images/'.$source.'" />';
 46    }
 47
 48As a matter of fact, the `image_tag()` function built into symfony is a little more complicated than that, as it accepts a second parameter to add other attributes to the `<img>` tag. You can check its complete syntax and options in the online [API documentation](http://www.symfony-project.org/api/1_4/).
 49
 50Most of the time, helpers carry intelligence and save you long and complex coding:
 51
 52    [php]
 53    <?php echo auto_link_text('Please visit our website www.example.com') ?>
 54     => Please visit our website <a href="http://www.example.com">www.example.com</a>
 55
 56Helpers facilitate the process of writing templates and produce the best possible HTML code in terms of performance and accessibility. You can always use plain HTML, but helpers are usually faster to write.
 57
 58>**TIP**
 59>You may wonder why the helpers are named according to the underscore syntax rather than the camelCase convention, used everywhere else in symfony. This is because helpers are functions, and all the core PHP functions use the underscore syntax convention.
 60
 61#### Declaring Helpers
 62
 63The symfony files containing helper definitions are not autoloaded (since they contain functions, not classes). Helpers are grouped by purpose. For instance, all the helper functions dealing with text are defined in a file called `TextHelper.php`, called the `Text` helper group. So if you need to use a helper in a template, you must load the related helper group earlier in the template by declaring it with the `use_helper()` function. Listing 7-3 shows a template using the `auto_link_text()` helper, which is part of the `Text` helper group.
 64
 65Listing 7-3 - Declaring the Use of a Helper
 66
 67    [php]
 68    // Use a specific helper group in this template
 69    <?php use_helper('Text') ?>
 70    ...
 71    <h1>Description</h1>
 72    <p><?php echo auto_link_text($description) ?></p>
 73
 74>**TIP**
 75>If you need to declare more than one helper group, add more arguments to the `use_helper()` call. For instance, to load both the `Text` and the `Javascript` helper groups in a template, call `<?php use_helper('Text', 'Javascript') ?>`.
 76
 77A few helpers are available by default in every template, without need for declaration. These are helpers of the following helper groups:
 78
 79  * `Helper`: Required for helper inclusion (the `use_helper()` function is, in fact, a helper itself)
 80  * `Tag`: Basic tag helper, used by almost every helper
 81  * `Url`: Links and URL management helpers
 82  * `Asset`: Helpers populating the HTML `<head>` section, and providing easy links to external assets (images, JavaScript, and style sheet files)
 83  * `Partial`: Helpers allowing for inclusion of template fragments
 84  * `Cache`: Manipulation of cached code fragments
 85
 86The list of the standard helpers, loaded by default for every template, is configurable in the `settings.yml` file. So if you know that you will not use the helpers of the `Cache` group, or that you will always use the ones of the Text group, modify the `standard_helpers` setting accordingly. This will speed up your application a bit. You cannot remove the first four helper groups in the preceding list (`Helper`, `Tag`, `Url`, and `Asset`), because they are compulsory for the templating engine to work properly. Consequently, they don't even appear in the list of standard helpers.
 87
 88>**TIP**
 89>If you ever need to use a helper outside a template, you can still load a helper group from anywhere by calling `sfProjectConfiguration::getActive()->loadHelpers($helpers)`, where `$helpers` is a helper group name or an array of helper group names. For instance, if you want to use `auto_link_text()` in an action, you need to call `sfProjectConfiguration::getActive()->loadHelpers('Text')` first.
 90
 91#### Frequently Used Helpers
 92
 93You will learn about some helpers in detail in later chapters, in relation with the feature they are helping. Listing 7-4 gives a brief list of the default helpers that are used a lot, together with the HTML code they return.
 94
 95Listing 7-4 - Common Default Helpers
 96
 97    [php]
 98    // Helper group
 99    <?php use_helper('HelperName') ?>
100    <?php use_helper('HelperName1', 'HelperName2', 'HelperName3') ?>
101
102    // Url group
103    <?php echo link_to('click me', 'mymodule/myaction') ?>
104    => <a href="/route/to/myaction">click me</a>  // Depends on the routing settings
105
106    // Asset group
107    <?php echo image_tag('myimage', 'alt=foo size=200x100') ?>
108     => <img src="/images/myimage.png" alt="foo" width="200" height="100"/>
109    <?php echo javascript_include_tag('myscript') ?>
110     => <script language="JavaScript" type="text/javascript" src="/js/myscript.js"></script>
111    <?php echo stylesheet_tag('style') ?>
112     => <link href="/stylesheets/style.css" media="screen" rel="stylesheet"type="text/css" />
113
114There are many other helpers in symfony, and it would take a full book to describe all of them. The best reference for helpers is the online [API documentation](http:// www.symfony-project.org/api/1_4/), where all the helpers are well documented, with their syntax, options, and examples.
115
116#### Adding Your Own Helpers
117
118Symfony ships with a lot of helpers for various purposes, but if you don't find what you need in the API documentation, you will probably want to create a new helper. This is very easy to do.
119
120Helper functions (regular PHP functions returning HTML code) should be saved in a file called `FooBarHelper.php`, where `FooBar` is the name of the helper group. Store the file in the `apps/frontend/lib/helper/` directory (or in any `helper/` directory created under one of the `lib/` folders of your project) so it can be found automatically by the `use_helper('FooBar')` helper for inclusion.
121
122>**TIP**
123>This system even allows you to override the existing symfony helpers. For instance, to redefine all the helpers of the `Text` helper group, just create a `TextHelper.php` file in your `apps/frontend/lib/helper/` directory. Whenever you call `use_helper('Text')`, symfony will use your helper group rather than its own. But be careful: as the original file is not even loaded, you must redefine all the functions of a helper group to override it; otherwise, some of the original helpers will not be available at all.
124
125### Page Layout
126
127The template shown in Listing 7-1 is not a valid XHTML document. The `DOCTYPE` definition and the `<html>` and `<body>` tags are missing. That's because they are stored somewhere else in the application, in a file called `layout.php`, which contains the page layout. This file, also called the global template, stores the HTML code that is common to all pages of the application to avoid repeating it in every template. The content of the template is integrated into the layout, or, if you change the point of view, the layout "decorates" the template. This is an application of the decorator design pattern, illustrated in Figure 7-1.
128
129>**TIP**
130>For more information about the decorator and other design patterns, see *Patterns of Enterprise Application Architecture* by Martin Fowler (Addison-Wesley, ISBN: 0-32112-742-0).
131
132Figure 7-1 - Decorating a template with a layout
133
134![Decorating a template with a layout](http://www.symfony-project.org/images/book/1_4/F0701.png "Decorating a template with a layout")
135
136Listing 7-5 shows the default page layout, located in the application `templates/` directory.
137
138Listing 7-5 - Default Layout, in `myproject/apps/frontend/templates/layout.php`
139
140    [php]
141    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
142    <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
143      <head>
144        <?php include_javascripts() ?>
145        <?php include_stylesheets() ?>
146        <?php include_http_metas() ?>
147        <?php include_metas() ?>
148        <?php include_title() ?>
149        <link rel="shortcut icon" href="/favicon.ico" />
150      </head>
151      <body>
152        <?php echo $sf_content ?>
153      </body>
154    </html>
155
156The helpers called in the `<head>` section grab information from the response object and the view configuration. The `<body>` tag outputs the result of the template. With this layout, the default configuration, and the sample template in Listing 7-1, the processed view looks like Listing 7-6.
157
158Listing 7-6 - The Layout, the View Configuration, and the Template Assembled
159
160    [php]
161    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
162    <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
163      <head>
164        <meta http-equiv="content-type" content="text/html; charset=utf-8" />
165        <meta name="title" content="symfony project" />
166        <meta name="robots" content="index, follow" />
167        <meta name="description" content="symfony project" />
168        <meta name="keywords" content="symfony, project" />
169        <title>symfony project</title>
170        <link rel="stylesheet" type="text/css" href="/css/main.css" />
171        <link rel="shortcut icon" href="/favicon.ico">
172      </head>
173      <body>
174        <h1>Welcome</h1>
175        <p>Welcome back, <?php echo $name ?>!</p>
176        <h2>What would you like to do?</h2>
177        <ul>
178          <li><?php echo link_to('Read the last articles', 'article/read') ?></li>
179          <li><?php echo link_to('Start writing a new one', 'article/write') ?></li>
180        </ul>
181      </body>
182    </html>
183
184The global template can be entirely customized for each application. Add in any HTML code you need. This layout is often used to hold the site navigation, logo, and so on. You can even have more than one layout, and decide which layout should be used for each action. Don't worry about JavaScript and style sheet inclusion for now; the "View Configuration" section later in this chapter shows how to handle that.
185
186### Template Shortcuts
187
188In templates, a few symfony variables are always available. These shortcuts give access to the most commonly needed information in templates, through the core symfony objects:
189
190  * `$sf_context`: The whole context object (`instance of sfContext`)
191  * `$sf_request`: The request object (`instance of sfRequest`)
192  * `$sf_params` : The parameters of the request object
193  * `$sf_user`   : The current user session object (`instance of sfUser`)
194
195The previous chapter detailed useful methods of the `sfRequest` and `sfUser` objects. You can actually call these methods in templates through the `$sf_request` and `$sf_user` variables. For instance, if the request includes a `total` parameter, its value is available in the template with the following:
196
197    [php]
198    // Long version
199    <?php echo $sf_request->getParameter('total') ?>
200
201    // Shorter version
202    <?php echo $sf_params->get('total') ?>
203
204    // Equivalent to the following action code
205    echo $request->getParameter('total')
206
207Code Fragments
208--------------
209
210You may often need to include some HTML or PHP code in several pages. To avoid repeating that code, the PHP `include()` statement will suffice most of the time.
211
212For instance, if many of the templates of your application need to use the same fragment of code, save it in a file called `myFragment.php` in the global template directory (`myproject/apps/frontend/templates/`) and include it in your templates as follows:
213
214    [php]
215    <?php include(sfConfig::get('sf_app_template_dir').'/myFragment.php') ?>
216
217But this is not a very clean way to package a fragment, mostly because you can have different variable names between the fragment and the various templates including it. In addition, the symfony cache system (described in Chapter 12) has no way to detect an include, so the fragment cannot be cached independently from the template. Symfony provides three alternative types of intelligent code fragments to replace `include`s:
218
219  * If the logic is lightweight, you will just want to include a template file having access to some data you pass to it. For that, you will use a partial.
220  * If the logic is heavier (for instance, if you need to access the data model and/or modify the content according to the session), you will prefer to separate the presentation from the logic. For that, you will use a component.
221  * If the fragment is meant to replace a specific part of the layout, for which default content may already exist, you will use a slot.
222
223The inclusion of these fragments is achieved by helpers of the `Partial` group. These helpers are available from any symfony template, without initial declaration.
224
225### Partials
226
227A partial is a reusable chunk of template code. For instance, in a publication application, the template code displaying an article is used in the article detail page, and also in the list of the best articles and the list of latest articles. This code is a perfect candidate for a partial, as illustrated in Figure 7-2.
228
229Figure 7-2 - Reusing partials in templates
230
231![Reusing partials in templates](http://www.symfony-project.org/images/book/1_4/F0702.png "Reusing partials in templates")
232
233Just like templates, partials are files located in the `templates/` directory, and they contain HTML code with embedded PHP. A partial file name always starts with an underscore (`_`), and that helps to distinguish partials from templates, since they are located in the same `templates/` folders.
234
235A template can include partials whether it is in the same module, in another module, or in the global `templates/` directory. Include a partial by using the `include_partial()` helper, and specify the module and partial name as a parameter (but omit the leading underscore and the trailing `.php`), as described in Listing 7-7.
236
237Listing 7-7 - Including a Partial in a Template of the `mymodule` Module
238
239    [php]
240    // Include the frontend/modules/mymodule/templates/_mypartial1.php partial
241    // As the template and the partial are in the same module,
242    // you can omit the module name
243    <?php include_partial('mypartial1') ?>
244
245    // Include the frontend/modules/foobar/templates/_mypartial2.php partial
246    // The module name is compulsory in that case
247    <?php include_partial('foobar/mypartial2') ?>
248
249    // Include the frontend/templates/_mypartial3.php partial
250    // It is considered as part of the 'global' module
251    <?php include_partial('global/mypartial3') ?>
252
253Partials have access to the usual symfony helpers and template shortcuts. But since partials can be called from anywhere in the application, they do not have automatic access to the variables defined in the action calling the templates that includes them, unless passed explicitly as an argument. For instance, if you want a partial to have access to a `$total` variable, the action must hand it to the template, and then the template to the helper as a second argument of the `include_partial()` call, as shown in Listings 7-8, 7-9, and 7-10.
254
255Listing 7-8 - The Action Defines a Variable, in `mymodule/actions/actions.class.php`
256
257    [php]
258    class mymoduleActions extends sfActions
259    {
260      public function executeIndex()
261      {
262        $this->total = 100;
263      }
264    }
265
266Listing 7-9 - The Template Passes the Variable to the Partial, in `mymodule/templates/indexSuccess.php`
267
268    [php]
269    <p>Hello, world!</p>
270    <?php include_partial('mypartial', array('mytotal' => $total)) ?>
271
272Listing 7-10 - The Partial Can Now Use the Variable, in `mymodule/templates/_mypartial.php`
273
274    [php]
275    <p>Total: <?php echo $mytotal ?></p>
276
277>**TIP**
278>All the helpers so far were called by `<?php echo functionName() ?>`. The partial helper, however, is simply called by `<?php include_partial() ?>`, without `echo`, to make it behave similar to the regular PHP `include()` statement. If you ever need a function that returns the content of a partial without actually displaying it, use `get_partial()` instead. All the `include_` helpers described in this chapter have a `get_` counterpart that can be called together with an `echo` statement.
279
280>**TIP**
281>Instead of resulting in a template, an action can return a partial or a component. The `renderPartial()` and `renderComponent()` methods of the action class promote reusability of code. Besides, they take advantage of the caching abilities of the partials (see Chapter 12). The variables defined in the action will be automatically passed to the partial/component, unless you define an associative array of variables as a second parameter of the method.
282>
283>     [php]
284>     public function executeFoo()
285>     {
286>       // do things
287>       $this->foo = 1234;
288>       $this->bar = 4567;
289>
290>       return $this->renderPartial('mymodule/mypartial');
291>     }
292>
293>In this example, the partial will have access to `$foo` and `$bar`. If the action ends with the following line:
294>
295>       return $this->renderPartial('mymodule/mypartial', array('foo' => $this->foo));
296>
297>Then the partial will only have access to `$foo`.
298
299### Components
300
301In Chapter 2, the first sample script was split into two parts to separate the logic from the presentation. Just like the MVC pattern applies to actions and templates, you may need to split a partial into a logic part and a presentation part. In such a case, you should use a component.
302
303A component is like an action, except it's much faster. The logic of a component is kept in a class inheriting from `sfComponents`, located in an `actions/components.class.php` file. Its presentation is kept in a partial. Methods of the `sfComponents` class start with the word `execute`, just like actions, and they can pass variables to their presentation counterpart in the same way that actions can pass variables. Partials that serve as presentation for components are named by the component (without the leading `execute`, but with an underscore instead). Table 7-1 compares the naming conventions for actions and components.
304
305Table 7-1 - Action and Component Naming Conventions
306
307Convention               |  Actions              |  Components
308------------------------ | --------------------- | ----------------------
309Logic file               | `actions.class.php`   | `components.class.php`
310Logic class extends      | `sfActions`           | `sfComponents`
311Method naming            | `executeMyAction()`   | `executeMyComponent()`
312Presentation file naming | `myActionSuccess.php` | `_myComponent.php`
313
314>**TIP**
315>Just as you can separate actions files, the `sfComponents` class has an `sfComponent` counterpart that allows for single component files with the same type of syntax.
316
317For instance, suppose you have a sidebar displaying the latest news headlines for a given subject, depending on the user's profile, which is reused in several pages. The queries necessary to get the news headlines are too complex to appear in a simple partial, so they need to be moved to an action-like file--a component. Figure 7-3 illustrates this example.
318
319For this example, shown in Listings 7-11 and 7-12, the component will be kept in its own module (called `news`), but you can mix components and actions in a single module if it makes sense from a functional point of view.
320
321Figure 7-3 - Using components in templates
322
323![Using components in templates](http://www.symfony-project.org/images/book/1_4/F0703.png "Using components in templates")
324
325Listing 7-11 - The Components Class, in `modules/news/actions/components.class.php`
326
327    [php]
328    <?php
329
330    class newsComponents extends sfComponents
331    {
332      public function executeHeadlines()
333      {
334        // Propel
335        $c = new Criteria();
336        $c->addDescendingOrderByColumn(NewsPeer::PUBLISHED_AT);
337        $c->setLimit(5);
338        $this->news = NewsPeer::doSelect($c);
339
340        // Doctrine
341        $query = Doctrine::getTable('News')
342                  ->createQuery()
343                  ->orderBy('published_at DESC')
344                  ->limit(5);
345
346        $this->news = $query->execute();
347      }
348    }
349
350Listing 7-12 - The Partial, in `modules/news/templates/_headlines.php`
351
352    [php]
353    <div>
354      <h1>Latest news</h1>
355      <ul>
356      <?php foreach($news as $headline): ?>
357        <li>
358          <?php echo $headline->getPublishedAt() ?>
359          <?php echo link_to($headline->getTitle(),'news/show?id='.$headline->getId()) ?>
360        </li>
361      <?php endforeach ?>
362      </ul>
363    </div>
364
365Now, every time you need the component in a template, just call this:
366
367    [php]
368    <?php include_component('news', 'headlines') ?>
369
370Just like the partials, components accept additional parameters in the shape of an associative array. The parameters are available to the partial under their name, and in the component via the `$this` object. See Listing 7-13 for an example.
371
372Listing 7-13 - Passing Parameters to a Component and Its Template
373
374    [php]
375    // Call to the component
376    <?php include_component('news', 'headlines', array('foo' => 'bar')) ?>
377
378    // In the component itself
379    echo $this->foo;
380     => 'bar'
381
382    // In the _headlines.php partial
383    echo $foo;
384     => 'bar'
385
386You can include components in components, or in the global layout, as in any regular template. Like actions, components' `execute` methods can pass variables to the related partial and have access to the same shortcuts. But the similarities stop there. A component doesn't handle security or validation, cannot be called from the Internet (only from the application itself), and doesn't have various return possibilities. That's why a component is faster to execute than an action.
387
388### Slots
389
390Partials and components are great for reusability. But in many cases, code fragments are required to fill a layout with more than one dynamic zone. For instance, suppose that you want to add some custom tags in the `<head>` section of the layout, depending on the content of the action. Or, suppose that the layout has one major dynamic zone, which is filled by the result of the action, plus a lot of other smaller ones, which have a default content defined in the layout but can be overridden at the template level.
391
392For these situations, the solution is a slot. Basically, a slot is a placeholder that you can put in any of the view elements (in the layout, a template, or a partial). Filling this placeholder is just like setting a variable. The filling code is stored globally in the response, so you can define it anywhere (in the layout, a template, or a partial). Just make sure to define a slot before including it, and remember that the layout is executed after the template (this is the decoration process), and the partials are executed when they are called in a template. Does it sound too abstract? Let's see an example.
393
394Imagine a layout with one zone for the template and two slots: one for the sidebar and the other for the footer. The slot values are defined in the templates. During the decoration process, the layout code wraps the template code, and the slots are filled with the previously defined values, as illustrated in Figure 7-4. The sidebar and the footer can then be contextual to the main action. This is like having a layout with more than one "hole".
395
396Figure 7-4 - Layout slots defined in a template
397
398![Layout slots defined in a template](http://www.symfony-project.org/images/book/1_4/F0704.png "Layout slots defined in a template")
399
400Seeing some code will clarify things further. To include a slot, use the `include_slot()` helper. The `has_slot()` helper returns `true` if the slot has been defined before, providing a fallback mechanism as a bonus. For instance, define a placeholder for a `'sidebar'` slot in the layout and its default content as shown in Listing 7-14.
401
402Listing 7-14 - Including a `'sidebar'` Slot in the Layout
403
404    [php]
405    <div id="sidebar">
406    <?php if (has_slot('sidebar')): ?>
407      <?php include_slot('sidebar') ?>
408    <?php else: ?>
409      <!-- default sidebar code -->
410      <h1>Contextual zone</h1>
411      <p>This zone contains links and information
412      relative to the main content of the page.</p>
413    <?php endif; ?>
414    </div>
415
416As it's quite common to display some default content if a slot is not defined, the `include_slot` helper returns a Boolean indicating if the slot has been defined. Listing 7-15 shows how to take this return value into account to simplify the code.
417
418Listing 7-15 - Including a `'sidebar'` Slot in the Layout
419
420    [php]
421    <div id="sidebar">
422    <?php if (!include_slot('sidebar')): ?>
423      <!-- default sidebar code -->
424      <h1>Contextual zone</h1>
425      <p>This zone contains links and information
426      relative to the main content of the page.</p>
427    <?php endif; ?>
428    </div>
429
430Each template has the ability to define the contents of a slot (actually, even partials can do it). As slots are meant to hold HTML code, symfony offers a convenient way to define them: just write the slot code between a call to the `slot()` and `end_slot()` helpers, as in Listing 7-16.
431
432Listing 7-16 - Overriding the `'sidebar'` Slot Content in a Template
433
434    [php]
435    // ...
436
437    <?php slot('sidebar') ?>
438      <!-- custom sidebar code for the current template-->
439      <h1>User details</h1>
440      <p>name:  <?php echo $user->getName() ?></p>
441      <p>email: <?php echo $user->getEmail() ?></p>
442    <?php end_slot() ?>
443
444The code between the slot helpers is executed in the context of the template, so it has access to all the variables that were defined in the action. Symfony will automatically put the result of this code in the response object. It will not be displayed in the template, but made available for future `include_slot()` calls, like the one in Listing 7-14.
445
446Slots are very useful to define zones meant to display contextual content. They can also be used to add HTML code to the layout for certain actions only. For instance, a template displaying the list of the latest news might want to add a link to an RSS feed in the `<head>` part of the layout. This is achieved simply by adding a `'feed'` slot in the layout and overriding it in the template of the list.
447
448If the content of the slot is very short, as this is the case when defining a `title` slot for example, you can simply pass the content as a second argument of the `slot()` method as shown in Listing 7-17.
449
450Listing 7-17 - Using `slot()` to define a short Value
451
452    [php]
453    <?php slot('title', 'The title value') ?>
454
455>**SIDEBAR**
456>Where to find template fragments
457>
458>People working on templates are usually web designers, who may not know symfony very well and may have difficulties finding template fragments, since they can be scattered all over the application. These few guidelines will make them more comfortable with the symfony templating system.
459>
460>First of all, although a symfony project contains many directories, all the layouts, templates, and template fragments files reside in directories named `templates/`. So as far as a web designer is concerned, a project structure can be reduced to something like this:
461>
462>
463>     myproject/
464>       apps/
465>         application1/
466>           templates/       # Layouts for application 1
467>           modules/
468>             module1/
469>               templates/   # Templates and partials for module 1
470>             module2/
471>               templates/   # Templates and partials for module 2
472>             module3/
473>               templates/   # Templates and partials for module 3
474>
475>
476>All other directories can be ignored.
477>
478>When meeting an `include_partial()`, web designers just need to understand that only the first argument is important. This argument's pattern is `module_name/partial_name`, and that means that the presentation code is to be found in `modules/module_name/templates/_partial_name.php`.
479>
480>For the `include_component()` helper, module name and partial name are the first two arguments. As for the rest, a general idea about what helpers are and which helpers are the most common in templates should be enough to start designing templates for symfony applications.
481
482View Configuration
483------------------
484
485In symfony, a view consists of two distinct parts:
486
487  * The HTML presentation of the action result (stored in the template, in the layout, and in the template fragments)
488  * All the rest, including the following:
489
490    * Meta declarations: Keywords, description, or cache duration.
491    * Page title: Not only does it help users with several browser windows open to find yours, but it is also very important for search sites' indexing.
492    * File inclusions: JavaScript and style sheet files.
493    * Layout: Some actions require a custom layout (pop-ups, ads, and so on) or no layout at all (such as Ajax actions).
494
495In the view, all that is not HTML is called view configuration, and symfony provides two ways to manipulate it. The usual way is through the `view.yml` configuration file. It can be used whenever the values don't depend on the context or on database queries. When you need to set dynamic values, the alternative method is to set the view configuration via the `sfResponse` object attributes directly in the action.
496
497>**NOTE**
498>If you ever set a view configuration parameter both via the `sfResponse` object and via the `view.yml` file, the `sfResponse` definition takes precedence.
499
500### The `view.yml` File
501
502Each module can have one `view.yml` file defining the settings of its views. This allows you to define view settings for a whole module and per view in a single file. The first-level keys of the `view.yml` file are the module view names. Listing 7-18 shows an example of view configuration.
503
504Listing 7-18 - Sample Module-Level `view.yml`
505
506    editSuccess:
507      metas:
508        title: Edit your profile
509
510    editError:
511      metas:
512        title: Error in the profile edition
513
514    all:
515      stylesheets: [my_style]
516      metas:
517        title: My website
518
519>**CAUTION**
520>Be aware that the main keys in the `view.yml` file are view names, not action names. As a reminder, a view name is composed of an action name and an action termination. For instance, if the `edit` action returns `sfView::SUCCESS` (or returns nothing at all, since it is the default action termination), then the view name is `editSuccess`.
521
522The default settings for the module are defined under the `all:` key in the module `view.yml`. The default settings for all the application views are defined in the application `view.yml`. Once again, you recognize the configuration cascade principle:
523
524  * In `apps/frontend/modules/mymodule/config/view.yml`, the per-view definitions apply only to one view and override the module-level definitions.
525  * In `apps/frontend/modules/mymodule/config/view.yml`, the `all:` definitions apply to all the actions of the module and override the application-level definitions.
526  * In `apps/frontend/config/view.yml`, the `default:` definitions apply to all modules and all actions of the application.
527
528>**TIP**
529>Module-level `view.yml` files don't exist by default. The first time you need to adjust a view configuration parameter for a module, you will have to create an empty `view.yml` in its `config/` directory.
530
531After seeing the default template in Listing 7-5 and an example of a final response in Listing 7-6, you may wonder where the header values come from. As a matter of fact, they are the default view settings, defined in the application `view.yml` and shown in Listing 7-19.
532
533Listing 7-19 - Default Application-Level View Configuration, in `apps/frontend/config/view.yml`
534
535    default:
536      http_metas:
537        content-type: text/html
538
539      metas:
540        #title:        symfony project
541        #description:  symfony project
542        #keywords:     symfony, project
543        #language:     en
544        #robots:       index, follow
545
546      stylesheets:    [main]
547
548      javascripts:    []
549
550      has_layout:     true
551      layout:         layout
552
553Each of these settings will be described in detail in the "View Configuration Settings" section.
554
555### The Response Object
556
557Although part of the view layer, the response object is often modified by the action. Actions can access the symfony response object, called `sfResponse`, via the `getResponse()` method. Listing 7-20 lists some of the `sfResponse` methods often used from within an action.
558
559Listing 7-20 - Actions Have Access to the `sfResponse` Object Methods
560
561    [php]
562    class mymoduleActions extends sfActions
563    {
564      public function executeIndex()
565      {
566        $response = $this->getResponse();
567
568        // HTTP headers
569        $response->setContentType('text/xml');
570        $response->setHttpHeader('Content-Language', 'en');
571        $response->setStatusCode(403);
572        $response->addVaryHttpHeader('Accept-Language');
573        $response->addCacheControlHttpHeader('no-cache');
574
575        // Cookies
576        $response->setCookie($name, $content, $expire, $path, $domain);
577
578        // Metas and page headers
579        $response->addMeta('robots', 'NONE');
580        $response->addMeta('keywords', 'foo bar');
581        $response->setTitle('My FooBar Page');
582        $response->addStyleSheet('custom_style');
583        $response->addJavaScript('custom_behavior');
584      }
585    }
586
587In addition to the setter methods shown here, the `sfResponse` class has getters that return the current value of the response attributes.
588
589The header setters are very powerful in symfony. Headers are sent as late as possible (in the `sfRenderingFilter`), so you can alter them as much as you want and as late as you want. They also provide very useful shortcuts. For instance, if you don't specify a charset when you call `setContentType()`, symfony automatically adds the default charset defined in the `settings.yml` file.
590
591    [php]
592    $response->setContentType('text/xml');
593    echo $response->getContentType();
594     => 'text/xml; charset=utf-8'
595
596The status code of responses in symfony is compliant with the HTTP specification. Exceptions return a status 500, pages not found return a status 404, normal pages return a status 200, pages not modified can be reduced to a simple header with status code 304 (see Chapter 12 for details), and so on. But you can override these defaults by setting your own status code in the action with the `setStatusCode()` response method. You can specify a custom code and a custom message, or simply a custom code--in which case, symfony will add the most common message for this code.
597
598    [php]
599    $response->setStatusCode(404, 'This page does not exist');
600
601>**TIP**
602>Before sending the headers, symfony normalizes their names. So you don't need to bother about writing `content-language` instead of `Content-Language` in a call to `setHttpHeader()`, as symfony will understand the former and automatically transform it to the latter.
603
604### View Configuration Settings
605
606You may have noticed that there are two kinds of view configuration settings:
607
608  * The ones that have a unique value (the value is a string in the `view.yml` file and the response uses a `set` method for those)
609  * The ones with multiple values (for which `view.yml` uses arrays and the response uses an `add` method)
610
611Keep in mind that the configuration cascade erases the unique value settings but piles up the multiple values settings. This will become more apparent as you progress through this chapter.
612
613#### Meta Tag Configuration
614
615The information written in the `<meta>` tags in the response is not displayed in a browser but is useful for robots and search engines. It also controls the cache settings of every page. Define these tags under the `http_metas:` and `metas:` keys in `view.yml`, as in Listing 7-21, or with the `addHttpMeta()` and `addMeta()` response methods in the action, as in Listing 7-22.
616
617Listing 7-21 - Meta Definition As Key: Value Pairs in `view.yml`
618
619    http_metas:
620      cache-control: public
621
622    metas:
623      description:   Finance in France
624      keywords:      finance, France
625
626Listing 7-22 - Meta Definition As Response Settings in the Action
627
628    [php]
629    $this->getResponse()->addHttpMeta('cache-control', 'public');
630    $this->getResponse()->addMeta('description', 'Finance in France');
631    $this->getResponse()->addMeta('keywords', 'finance, France');
632
633Adding an existing key will replace its current content by default. For HTTP meta tags, you can add a third parameter and set it to `false` to have the `addHttpMeta()` method (as well as the `setHttpHeader()`) append the value to the existing one, rather than replacing it.
634
635    [php]
636    $this->getResponse()->addHttpMeta('accept-language', 'en');
637    $this->getResponse()->addHttpMeta('accept-language', 'fr', false);
638    echo $this->getResponse()->getHttpHeader('accept-language');
639     => 'en, fr'
640
641In order to have these meta tags appear in the final document, the `include_http_metas()` and `include_metas()` helpers must be called in the `<head>` section (this is the case in the default layout; see Listing 7-5). Symfony automatically aggregates the settings from all the `view.yml` files (including the default one shown in Listing 7-18) and the response attribute to output proper `<meta>` tags. The example in Listing 7-21 ends up as shown in Listing 7-23.
642
643Listing 7-23 - Meta Tags Output in the Final Page
644
645    [php]
646    <meta http-equiv="content-type" content="text/html; charset=utf-8" />
647    <meta http-equiv="cache-control" content="public" />
648    <meta name="robots" content="index, follow" />
649    <meta name="description" content="Finance in France" />
650    <meta name="keywords" content="finance, France" />
651
652As a bonus, the HTTP header of the response is also impacted by the `http-metas:` definition, even if you don't have any `include_http_metas()` helpers in the layout, or if you have no layout at all. For instance, if you need to send a page as plain text, define the following `view.yml`:
653
654    http_metas:
655      content-type: text/plain
656
657    has_layout: false
658
659#### Title Configuration
660
661The page title is a key part to search engine indexing. It is also very useful with modern browsers that provide tabbed browsing. In HTML, the title is both a tag and meta information of the page, so the `view.yml` file sees the `title:` key as a child of the `metas:` key. Listing 7-24 shows the title definition in `view.yml`, and Listing 7-25 shows the definition in the action.
662
663Listing 7-24 - Title Definition in `view.yml`
664
665    indexSuccess:
666      metas:
667        title: Three little piggies
668
669Listing 7-25 - Title Definition in the Action--Allows for Dynamic Titles
670
671    [php]
672    $this->getResponse()->setTitle(sprintf('%d little piggies', $number));
673
674In the `<head>` section of the final document, the title definition sets the `<meta name="title">` tag if the `include_metas()` helper is present, and the `<title>` tag if the `include_title()` helper is present. If both are included (as in the default layout of Listing 7-5), the title appears twice in the document source (see Listing 7-6), which is harmless.
675
676>**TIP**
677>Another way to handle the title definition is to use slots, as discussed above. This method allow to keep a better separation of concern between controllers and templates : the title belongs to the view, not the controller.
678
679#### File Inclusion Configuration
680
681Adding a specific style sheet or JavaScript file to a view is easy, as Listing 7-26 demonstrates.
682
683Listing 7-26 - Asset File Inclusion
684
685    [yml]
686    // In the view.yml
687    indexSuccess:
688      stylesheets: [mystyle1, mystyle2]
689      javascripts: [myscript]
690      
691-
692
693    [php]
694    // In the action
695    $this->getResponse()->addStylesheet('mystyle1');
696    $this->getResponse()->addStylesheet('mystyle2');
697    $this->getResponse()->addJavascript('myscript');
698
699    // In the Template
700    <?php use_stylesheet('mystyle1') ?>
701    <?php use_stylesheet('mystyle2') ?>
702    <?php use_javascript('myscript') ?>
703    
704In each case, the argument is a file name. If the file has a logical extension (`.css` for a style sheet and `.js` for a JavaScript file), you can omit it. If the file has a logical location (`/css/` for a style sheet and `/js/` for a JavaScript file), you can omit it as well. Symfony is smart enough to figure out the correct extension or location.
705
706Like the meta and title definitions, the file inclusion definitions require the usage of the `include_javascripts()` and `include_stylesheets()` helpers in the template or layout to be included. This means that the previous settings will output the HTML code of Listing 7-27.
707
708Listing 7-27 - File Inclusion Result
709
710    [php]
711    <head>
712    ...
713    <link rel="stylesheet" type="text/css" media="screen" href="/css/mystyle1.css" />
714    <link rel="stylesheet" type="text/css" media="screen" href="/css/mystyle2.css" />
715    <script language="javascript" type="text/javascript" src="/js/myscript.js">
716    </script>
717    </head>
718
719Remember that the configuration cascade principle applies, so any file inclusion defined in the application `view.yml` makes it appear in every page of the application. Listings 7-28, 7-29, and 7-30 demonstrate this principle.
720
721Listing 7-28 - Sample Application `view.yml`
722
723    default:
724      stylesheets: [main]
725
726Listing 7-29 - Sample Module `view.yml`
727
728    indexSuccess:
729      stylesheets: [special]
730
731    all:
732      stylesheets: [additional]
733
734Listing 7-30 - Resulting `indexSuccess` View
735
736    [php]
737    <link rel="stylesheet" type="text/css" media="screen" href="/css/main.css" />
738    <link rel="stylesheet" type="text/css" media="screen" href="/css/additional.css" />
739    <link rel="stylesheet" type="text/css" media="screen" href="/css/special.css" />
740
741If you need to remove a file defined at a higher level, just add a minus sign (`-`) in front of the file name in the lower-level definition, as shown in Listing 7-31.
742
743Listing 7-31 - Sample Module `view.yml` That Removes a File Defined at the Application Level
744
745    indexSuccess:
746      stylesheets: [-main, special]
747
748    all:
749      stylesheets: [additional]
750
751To remove all style sheets or JavaScript files, use `-*` as a file name, as shown in Listing 7-32.
752
753Listing 7-32 - Sample Module `view.yml` That Removes all Files Defined at the Application Level
754
755    indexSuccess:
756      stylesheets: [-*]
757      javascripts: [-*]
758
759You can be more accurate and define an additional parameter to force the position where to include the file (first or last position), as shown in Listing 7-33. This works for both style sheets and JavaScript files.
760
761Listing 7-33 - Defining the Position of the Included Asset
762
763    [yml]
764    // In the view.yml
765    indexSuccess:
766      stylesheets: [special: { position: first }]
767
768-
769    
770    [php]
771    // In the action
772    $this->getResponse()->addStylesheet('special', 'first');
773    
774    // In the template
775    <?php use_stylesheet('special', 'first') ?>
776
777You can also decide to bypass the transformation of the asset file name, so that the resulting `<link>` or `<script>` tags refer to the exact location specified, as show in Listing 7-34.
778
779Listing 7-34 - Style Sheet Inclusion with Raw Name
780
781    [yml]
782    // In the view.yml
783    indexSuccess:
784      stylesheets: [main, paper: { raw_name: true }]
785
786-
787    
788    [php]
789    // In the Action
790    $this->getResponse()->addStylesheet('main', '', array('raw_name' => true));
791    
792    // In the template
793    <?php use_stylesheet('main', '', array('raw_name' => true)) ?>
794    
795    // Resulting View
796    <link rel="stylesheet" type="text/css" href="main" />
797
798To specify media for a style sheet inclusion, you can change the default style sheet tag options, as shown in Listing 7-35.
799
800Listing 7-35 - Style Sheet Inclusion with Media
801
802    [yml]
803    // In the view.yml
804    indexSuccess:
805      stylesheets: [main, paper: { media: print }]
806
807-
808    
809    [php]
810    // In the Action
811    $this->getResponse()->addStylesheet('paper', '', array('media' => 'print'));
812    
813    // In the template
814    <?php use_stylesheet('paper', '', array('media' => 'print')) ?>
815    
816    // Resulting View
817    <link rel="stylesheet" type="text/css" media="print" href="/css/paper.css" />
818
819>**SIDEBAR**
820>Note about assets inclusions using the view.yml file
821>
822>The best practice is to define the defaults stylesheets and javascripts file in the project view.yml file, and include specifics stylesheets or javascripts files in your templates using the dedicated helper. This way, you do not have to remove or replace already included assets, which can be a painfull in some cases.
823
824#### Layout Configuration
825
826According to the graphical charter of your website, you may have several layouts. Classic websites have at least two: the default layout and the pop-up layout.
827
828You have already seen that the default layout is `myproject/apps/frontend/templates/layout.php`. Additional layouts must be added in the same global `templates/` directory. If you want a view to use a `frontend/templates/my_layout.php` file, use the syntax shown in Listing 7-36.
829
830Listing 7-36 - Layout Definition
831
832    [yml]
833    // In view.yml
834    indexSuccess:
835      layout: my_layout
836
837-
838
839    [php]
840    // In the action
841    $this->setLayout('my_layout');
842    
843    // In the template
844    <?php decorate_with('my_layout') ?>
845
846Some views don't need any layout at all (for instance, plain text pages or RSS feeds). In that case, set `has_layout` to `false`, as shown in Listing 7-37.
847
848Listing 7-37 - Layout Removal 
849
850    [yml]
851    // In `view.yml`
852    indexSuccess:
853      has_layout: false
854    
855-
856
857    [php]
858    // In the Action
859    $this->setLayout(false);
860    
861    // In the template
862    <?php decorate_with(false) ?>
863
864>**NOTE**
865>Ajax actions views have no layout by default.
866
867Output Escaping
868---------------
869
870When you insert dynamic data in a template, you must be sure about the data integrity. For instance, if data comes from forms filled in by anonymous users, there is a risk that it may include malicious scripts intended to launch cross-site scripting (XSS) attacks. You must be able to escape the output data, so that any HTML tag it contains becomes harmless.
871
872As an example, suppose that a user fills an input field with the following value:
873
874    [php]
875    <script>alert(document.cookie)</script>
876
877If you echo this value without caution, the JavaScript will execute on every browser and allow for much more dangerous attacks than just displaying an alert. This is why you must escape the value before displaying it, so that it becomes something like this:
878
879    [php]
880    &lt;script&gt;alert(document.cookie)&lt;/script&gt;
881
882You could escape your output manually by enclosing every unsure value in a call to `htmlspecialchars()`, but that approach would be very repetitive and error-prone. Instead, symfony provides a special system, called output escaping, which automatically escapes every variable output in a template. It is activated by default in the application `settings.yml`.
883
884### Activating Output Escaping
885
886Output escaping is configured globally for an application in the `settings.yml` file. Two parameters control the way that output escaping works: the strategy determines how the variables are made available to the view, and the method is the default escaping function applied to the data.
887
888Basically, all you need to do to activate output escaping is to set the `escaping_strategy` parameter to `true` (which is the default), as shown in Listing 7-38.
889
890Listing 7-38 - Activating Output Escaping, in `frontend/config/settings.yml`
891
892    all:
893      .settings:
894        escaping_strategy: true
895        escaping_method:   ESC_SPECIALCHARS
896
897This wi…

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