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Relevant Search: With Applications for Solr and Elasticsearch

For more in depth reading about search, ranking and generally everything you could ever want to know about how lucene, elasticsearch or solr work under the hood I highly suggest this book. Easily one of the most interesting technical books I have read in a long time. If you are tasked with solving search relevance problems even if not in Solr or Elasticsearch it should be your first reference. Amazon Affiliate Link
https://bitbucket.org/bo_hmb/bo_hmb
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353<li class="toctree-l2"><a class="reference internal" href="../database/metadata.html">Getting MetaData</a></li>
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355<li class="toctree-l2"><a class="reference internal" href="../database/caching.html">Query Caching</a></li>
356<li class="toctree-l2"><a class="reference internal" href="../database/forge.html">Database Manipulation with Database Forge</a></li>
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358<li class="toctree-l2"><a class="reference internal" href="../database/db_driver_reference.html">Database Driver Reference</a></li>
359</ul>
360</li>
361</ul>
362<ul>
363<li class="toctree-l1"><a class="reference internal" href="../helpers/index.html">Helpers</a><ul>
364<li class="toctree-l2"><a class="reference internal" href="../helpers/array_helper.html">Array Helper</a></li>
365<li class="toctree-l2"><a class="reference internal" href="../helpers/captcha_helper.html">CAPTCHA Helper</a></li>
366<li class="toctree-l2"><a class="reference internal" href="../helpers/cookie_helper.html">Cookie Helper</a></li>
367<li class="toctree-l2"><a class="reference internal" href="../helpers/date_helper.html">Date Helper</a></li>
368<li class="toctree-l2"><a class="reference internal" href="../helpers/directory_helper.html">Directory Helper</a></li>
369<li class="toctree-l2"><a class="reference internal" href="../helpers/download_helper.html">Download Helper</a></li>
370<li class="toctree-l2"><a class="reference internal" href="../helpers/email_helper.html">Email Helper</a></li>
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372<li class="toctree-l2"><a class="reference internal" href="../helpers/form_helper.html">Form Helper</a></li>
373<li class="toctree-l2"><a class="reference internal" href="../helpers/html_helper.html">HTML Helper</a></li>
374<li class="toctree-l2"><a class="reference internal" href="../helpers/inflector_helper.html">Inflector Helper</a></li>
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378<li class="toctree-l2"><a class="reference internal" href="../helpers/security_helper.html">Security Helper</a></li>
379<li class="toctree-l2"><a class="reference internal" href="../helpers/smiley_helper.html">Smiley Helper</a></li>
380<li class="toctree-l2"><a class="reference internal" href="../helpers/string_helper.html">String Helper</a></li>
381<li class="toctree-l2"><a class="reference internal" href="../helpers/text_helper.html">Text Helper</a></li>
382<li class="toctree-l2"><a class="reference internal" href="../helpers/typography_helper.html">Typography Helper</a></li>
383<li class="toctree-l2"><a class="reference internal" href="../helpers/url_helper.html">URL Helper</a></li>
384<li class="toctree-l2"><a class="reference internal" href="../helpers/xml_helper.html">XML Helper</a></li>
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425  <div class="section" id="helper-functions">
426<h1>Helper Functions<a class="headerlink" href="#helper-functions" title="Permalink to this headline"></a></h1>
427<p>Helpers, as the name suggests, help you with tasks. Each helper file is
428simply a collection of functions in a particular category. There are <strong>URL
429Helpers</strong>, that assist in creating links, there are Form Helpers that help
430you create form elements, <strong>Text Helpers</strong> perform various text formatting
431routines, <strong>Cookie Helpers</strong> set and read cookies, File Helpers help you
432deal with files, etc.</p>
433<p>Unlike most other systems in CodeIgniter, Helpers are not written in an
434Object Oriented format. They are simple, procedural functions. Each
435helper function performs one specific task, with no dependence on other
436functions.</p>
437<p>CodeIgniter does not load Helper Files by default, so the first step in
438using a Helper is to load it. Once loaded, it becomes globally available
439in your <a class="reference internal" href="controllers.html"><span class="doc">controller</span></a> and
440<a class="reference internal" href="views.html"><span class="doc">views</span></a>.</p>
441<p>Helpers are typically stored in your <strong>system/helpers</strong>, or
442<strong>application/helpers directory</strong>. CodeIgniter will look first in your
443<strong>application/helpers directory</strong>. If the directory does not exist or the
444specified helper is not located there CI will instead look in your
445global <em>system/helpers/</em> directory.</p>
446<div class="section" id="loading-a-helper">
447<h2>Loading a Helper<a class="headerlink" href="#loading-a-helper" title="Permalink to this headline"></a></h2>
448<p>Loading a helper file is quite simple using the following method:</p>
449<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">load</span><span class="o">-&gt;</span><span class="na">helper</span><span class="p">(</span><span class="s1">&#39;name&#39;</span><span class="p">);</span>
450</pre></div>
451</div>
452<p>Where <strong>name</strong> is the file name of the helper, without the .php file
453extension or the “helper” part.</p>
454<p>For example, to load the <strong>URL Helper</strong> file, which is named
455<strong>url_helper.php</strong>, you would do this:</p>
456<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">load</span><span class="o">-&gt;</span><span class="na">helper</span><span class="p">(</span><span class="s1">&#39;url&#39;</span><span class="p">);</span>
457</pre></div>
458</div>
459<p>A helper can be loaded anywhere within your controller methods (or
460even within your View files, although that’s not a good practice), as
461long as you load it before you use it. You can load your helpers in your
462controller constructor so that they become available automatically in
463any function, or you can load a helper in a specific function that needs
464it.</p>
465<div class="admonition note">
466<p class="first admonition-title">Note</p>
467<p class="last">The Helper loading method above does not return a value, so
468don’t try to assign it to a variable. Just use it as shown.</p>
469</div>
470</div>
471<div class="section" id="loading-multiple-helpers">
472<h2>Loading Multiple Helpers<a class="headerlink" href="#loading-multiple-helpers" title="Permalink to this headline"></a></h2>
473<p>If you need to load more than one helper you can specify them in an
474array, like this:</p>
475<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">load</span><span class="o">-&gt;</span><span class="na">helper</span><span class="p">(</span>
476        <span class="k">array</span><span class="p">(</span><span class="s1">&#39;helper1&#39;</span><span class="p">,</span> <span class="s1">&#39;helper2&#39;</span><span class="p">,</span> <span class="s1">&#39;helper3&#39;</span><span class="p">)</span>
477<span class="p">);</span>
478</pre></div>
479</div>
480</div>
481<div class="section" id="auto-loading-helpers">
482<h2>Auto-loading Helpers<a class="headerlink" href="#auto-loading-helpers" title="Permalink to this headline"></a></h2>
483<p>If you find that you need a particular helper globally throughout your
484application, you can tell CodeIgniter to auto-load it during system
485initialization. This is done by opening the <strong>application/config/autoload.php</strong>
486file and adding the helper to the autoload array.</p>
487</div>
488<div class="section" id="using-a-helper">
489<h2>Using a Helper<a class="headerlink" href="#using-a-helper" title="Permalink to this headline"></a></h2>
490<p>Once you’ve loaded the Helper File containing the function you intend to
491use, you’ll call it the way you would a standard PHP function.</p>
492<p>For example, to create a link using the <code class="docutils literal"><span class="pre">anchor()</span></code> function in one of
493your view files you would do this:</p>
494<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="o">&lt;?</span><span class="nx">php</span> <span class="k">echo</span> <span class="nx">anchor</span><span class="p">(</span><span class="s1">&#39;blog/comments&#39;</span><span class="p">,</span> <span class="s1">&#39;Click Here&#39;</span><span class="p">);</span><span class="cp">?&gt;</span>
495</pre></div>
496</div>
497<p>Where “Click Here” is the name of the link, and “blog/comments” is the
498URI to the controller/method you wish to link to.</p>
499</div>
500<div class="section" id="extending-helpers">
501<h2>“Extending” Helpers<a class="headerlink" href="#extending-helpers" title="Permalink to this headline"></a></h2>
502<p>To “extend” Helpers, create a file in your <strong>application/helpers/</strong> folder
503with an identical name to the existing Helper, but prefixed with <strong>MY_</strong>
504(this item is configurable. See below.).</p>
505<p>If all you need to do is add some functionality to an existing helper -
506perhaps add a function or two, or change how a particular helper
507function operates - then it’s overkill to replace the entire helper with
508your version. In this case it’s better to simply “extend” the Helper.</p>
509<div class="admonition note">
510<p class="first admonition-title">Note</p>
511<p class="last">The term “extend” is used loosely since Helper functions are
512procedural and discrete and cannot be extended in the traditional
513programmatic sense. Under the hood, this gives you the ability to
514add to or or to replace the functions a Helper provides.</p>
515</div>
516<p>For example, to extend the native <strong>Array Helper</strong> you’ll create a file
517named <strong>application/helpers/MY_array_helper.php</strong>, and add or override
518functions:</p>
519<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// any_in_array() is not in the Array Helper, so it defines a new function</span>
520<span class="k">function</span> <span class="nf">any_in_array</span><span class="p">(</span><span class="nv">$needle</span><span class="p">,</span> <span class="nv">$haystack</span><span class="p">)</span>
521<span class="p">{</span>
522        <span class="nv">$needle</span> <span class="o">=</span> <span class="nb">is_array</span><span class="p">(</span><span class="nv">$needle</span><span class="p">)</span> <span class="o">?</span> <span class="nv">$needle</span> <span class="o">:</span> <span class="k">array</span><span class="p">(</span><span class="nv">$needle</span><span class="p">);</span>
523
524        <span class="k">foreach</span> <span class="p">(</span><span class="nv">$needle</span> <span class="k">as</span> <span class="nv">$item</span><span class="p">)</span>
525        <span class="p">{</span>
526                <span class="k">if</span> <span class="p">(</span><span class="nb">in_array</span><span class="p">(</span><span class="nv">$item</span><span class="p">,</span> <span class="nv">$haystack</span><span class="p">))</span>
527                <span class="p">{</span>
528                        <span class="k">return</span> <span class="k">TRUE</span><span class="p">;</span>
529                <span class="p">}</span>
530        <span class="p">}</span>
531
532        <span class="k">return</span> <span class="k">FALSE</span><span class="p">;</span>
533<span class="p">}</span>
534
535<span class="c1">// random_element() is included in Array Helper, so it overrides the native function</span>
536<span class="k">function</span> <span class="nf">random_element</span><span class="p">(</span><span class="nv">$array</span><span class="p">)</span>
537<span class="p">{</span>
538        <span class="nb">shuffle</span><span class="p">(</span><span class="nv">$array</span><span class="p">);</span>
539        <span class="k">return</span> <span class="nb">array_pop</span><span class="p">(</span><span class="nv">$array</span><span class="p">);</span>
540<span class="p">}</span>
541</pre></div>
542</div>
543<div class="section" id="setting-your-own-prefix">
544<h3>Setting Your Own Prefix<a class="headerlink" href="#setting-your-own-prefix" title="Permalink to this headline"></a></h3>
545<p>The filename prefix for “extending” Helpers is the same used to extend
546libraries and core classes. To set your own prefix, open your
547<strong>application/config/config.php</strong> file and look for this item:</p>
548<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$config</span><span class="p">[</span><span class="s1">&#39;subclass_prefix&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;MY_&#39;</span><span class="p">;</span>
549</pre></div>
550</div>
551<p>Please note that all native CodeIgniter libraries are prefixed with <strong>CI_</strong>
552so DO NOT use that as your prefix.</p>
553</div>
554</div>
555<div class="section" id="now-what">
556<h2>Now What?<a class="headerlink" href="#now-what" title="Permalink to this headline"></a></h2>
557<p>In the Table of Contents you’ll find a list of all the available Helper
558Files. Browse each one to see what they do.</p>
559</div>
560</div>
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