/wp-includes/template.php

<?php
/**
 * Template loading functions.
 *
 * @package WordPress
 * @subpackage Template
 */

/**
 * Retrieve path to a template
 *
 * Used to quickly retrieve the path of a template without including the file
 * extension. It will also check the parent theme, if the file exists, with
 * the use of {@link locate_template()}. Allows for more generic template location
 * without the use of the other get_*_template() functions.
 *
 * @since 1.5.0
 *
 * @param string $type Filename without extension.
 * @param array $templates An optional list of template candidates
 * @return string Full path to file.
 */
function get_query_template( $type, $templates = array() ) {
	$type = preg_replace( '|[^a-z0-9-]+|', '', $type );

	if ( empty( $templates ) )
		$templates = array("{$type}.php");

	return apply_filters( "{$type}_template", locate_template( $templates ) );
}

/**
 * Retrieve path of index template in current or parent template.
 *
 * @since 3.0.0
 *
 * @return string
 */
function get_index_template() {
	return get_query_template('index');
}

/**
 * Retrieve path of 404 template in current or parent template.
 *
 * @since 1.5.0
 *
 * @return string
 */
function get_404_template() {
	return get_query_template('404');
}

/**
 * Retrieve path of archive template in current or parent template.
 *
 * @since 1.5.0
 *
 * @return string
 */
function get_archive_template() {
	$post_types = array_filter( (array) get_query_var( 'post_type' ) );

	$templates = array();

	if ( count( $post_types ) == 1 ) {
		$post_type = reset( $post_types );
		$templates[] = "archive-{$post_type}.php";
	}
	$templates[] = 'archive.php';

	return get_query_template( 'archive', $templates );
}

/**
 * Retrieve path of author template in current or parent template.
 *
 * @since 1.5.0
 *
 * @return string
 */
function get_author_template() {
	$author = get_queried_object();

	$templates = array();

	if ( $author ) {
		$templates[] = "author-{$author->user_nicename}.php";
		$templates[] = "author-{$author->ID}.php";
	}
	$templates[] = 'author.php';

	return get_query_template( 'author', $templates );
}

/**
 * Retrieve path of category template in current or parent template.
 *
 * Works by first retrieving the current slug for example 'category-default.php' and then
 * trying category ID, for example 'category-1.php' and will finally fallback to category.php
 * template, if those files don't exist.
 *
 * @since 1.5.0
 * @uses apply_filters() Calls 'category_template' on file path of category template.
 *
 * @return string
 */
function get_category_template() {
	$category = get_queried_object();

	$templates = array();

	if ( $category ) {
		$templates[] = "category-{$category->slug}.php";
		$templates[] = "category-{$category->term_id}.php";
	}
	$templates[] = 'category.php';

	return get_query_template( 'category', $templates );
}

/**
 * Retrieve path of tag template in current or parent template.
 *
 * Works by first retrieving the current tag name, for example 'tag-wordpress.php' and then
 * trying tag ID, for example 'tag-1.php' and will finally fallback to tag.php
 * template, if those files don't exist.
 *
 * @since 2.3.0
 * @uses apply_filters() Calls 'tag_template' on file path of tag template.
 *
 * @return string
 */
function get_tag_template() {
	$tag = get_queried_object();

	$templates = array();

	if ( $tag ) {
		$templates[] = "tag-{$tag->slug}.php";
		$templates[] = "tag-{$tag->term_id}.php";
	}
	$templates[] = 'tag.php';

	return get_query_template( 'tag', $templates );
}

/**
 * Retrieve path of taxonomy template in current or parent template.
 *
 * Retrieves the taxonomy and term, if term is available. The template is
 * prepended with 'taxonomy-' and followed by both the taxonomy string and
 * the taxonomy string followed by a dash and then followed by the term.
 *
 * The taxonomy and term template is checked and used first, if it exists.
 * Second, just the taxonomy template is checked, and then finally, taxonomy.php
 * template is used. If none of the files exist, then it will fall back on to
 * index.php.
 *
 * @since 2.5.0
 * @uses apply_filters() Calls 'taxonomy_template' filter on found path.
 *
 * @return string
 */
function get_taxonomy_template() {
	$term = get_queried_object();

	$templates = array();

	if ( $term ) {
		$taxonomy = $term->taxonomy;
		$templates[] = "taxonomy-$taxonomy-{$term->slug}.php";
		$templates[] = "taxonomy-$taxonomy.php";
	}
	$templates[] = 'taxonomy.php';

	return get_query_template( 'taxonomy', $templates );
}

/**
 * Retrieve path of date template in current or parent template.
 *
 * @since 1.5.0
 *
 * @return string
 */
function get_date_template() {
	return get_query_template('date');
}

/**
 * Retrieve path of home template in current or parent template.
 *
 * This is the template used for the page containing the blog posts
 *
 * Attempts to locate 'home.php' first before falling back to 'index.php'.
 *
 * @since 1.5.0
 * @uses apply_filters() Calls 'home_template' on file path of home template.
 *
 * @return string
 */
function get_home_template() {
	$templates = array( 'home.php', 'index.php' );

	return get_query_template( 'home', $templates );
}

/**
 * Retrieve path of front-page template in current or parent template.
 *
 * Looks for 'front-page.php'.
 *
 * @since 3.0.0
 * @uses apply_filters() Calls 'front_page_template' on file path of template.
 *
 * @return string
 */
function get_front_page_template() {
	$templates = array('front-page.php');

	return get_query_template( 'front_page', $templates );
}

/**
 * Retrieve path of page template in current or parent template.
 *
 * Will first look for the specifically assigned page template
 * The will search for 'page-{slug}.php' followed by 'page-id.php'
 * and finally 'page.php'
 *
 * @since 1.5.0
 *
 * @return string
 */
function get_page_template() {
	$id = get_queried_object_id();
	$template = get_page_template_slug();
	$pagename = get_query_var('pagename');

	if ( ! $pagename && $id ) {
		// If a static page is set as the front page, $pagename will not be set. Retrieve it from the queried object
		$post = get_queried_object();
		$pagename = $post->post_name;
	}

	$templates = array();
	if ( $template && 0 === validate_file( $template ) )
		$templates[] = $template;
	if ( $pagename )
		$templates[] = "page-$pagename.php";
	if ( $id )
		$templates[] = "page-$id.php";
	$templates[] = 'page.php';

	return get_query_template( 'page', $templates );
}

/**
 * Retrieve path of paged template in current or parent template.
 *
 * @since 1.5.0
 *
 * @return string
 */
function get_paged_template() {
	return get_query_template('paged');
}

/**
 * Retrieve path of search template in current or parent template.
 *
 * @since 1.5.0
 *
 * @return string
 */
function get_search_template() {
	return get_query_template('search');
}

/**
 * Retrieve path of single template in current or parent template.
 *
 * @since 1.5.0
 *
 * @return string
 */
function get_single_template() {
	$object = get_queried_object();

	$templates = array();

	if ( $object )
		$templates[] = "single-{$object->post_type}.php";
	$templates[] = "single.php";

	return get_query_template( 'single', $templates );
}

/**
 * Retrieve path of attachment template in current or parent template.
 *
 * The attachment path first checks if the first part of the mime type exists.
 * The second check is for the second part of the mime type. The last check is
 * for both types separated by an underscore. If neither are found then the file
 * 'attachment.php' is checked and returned.
 *
 * Some examples for the 'text/plain' mime type are 'text.php', 'plain.php', and
 * finally 'text_plain.php'.
 *
 * @since 2.0.0
 *
 * @return string
 */
function get_attachment_template() {
	global $posts;

	if ( ! empty( $posts ) && isset( $posts[0]->post_mime_type ) ) {
		$type = explode( '/', $posts[0]->post_mime_type );

		if ( ! empty( $type ) ) {
			if ( $template = get_query_template( $type[0] ) )
				return $template;
			elseif ( $template = get_query_template( $type[1] ) )
				return $template;
			elseif ( $template = get_query_template( "$type[0]_$type[1]" ) )
				return $template;
		}
	}

	return get_query_template( 'attachment' );
}

/**
 * Retrieve path of comment popup template in current or parent template.
 *
 * Checks for comment popup template in current template, if it exists or in the
 * parent template.
 *
 * @since 1.5.0
 * @uses apply_filters() Calls 'comments_popup_template' filter on path.
 *
 * @return string
 */
function get_comments_popup_template() {
	$template = get_query_template( 'comments_popup', array( 'comments-popup.php' ) );

	// Backward compat code will be removed in a future release
	if ('' == $template)
		$template = ABSPATH . WPINC . '/theme-compat/comments-popup.php';

	return $template;
}

/**
 * Retrieve the name of the highest priority template file that exists.
 *
 * Searches in the STYLESHEETPATH before TEMPLATEPATH so that themes which
 * inherit from a parent theme can just overload one file.
 *
 * @since 2.7.0
 *
 * @param string|array $template_names Template file(s) to search for, in order.
 * @param bool $load If true the template file will be loaded if it is found.
 * @param bool $require_once Whether to require_once or require. Default true. Has no effect if $load is false.
 * @return string The template filename if one is located.
 */
function locate_template($template_names, $load = false, $require_once = true ) {
	$located = '';
	foreach ( (array) $template_names as $template_name ) {
		if ( !$template_name )
			continue;
		if ( file_exists(STYLESHEETPATH . '/' . $template_name)) {
			$located = STYLESHEETPATH . '/' . $template_name;
			break;
		} else if ( file_exists(TEMPLATEPATH . '/' . $template_name) ) {
			$located = TEMPLATEPATH . '/' . $template_name;
			break;
		}
	}

	if ( $load && '' != $located )
		load_template( $located, $require_once );

	return $located;
}

/**
 * Require the template file with WordPress environment.
 *
 * The globals are set up for the template file to ensure that the WordPress
 * environment is available from within the function. The query variables are
 * also available.
 *
 * @since 1.5.0
 *
 * @param string $_template_file Path to template file.
 * @param bool $require_once Whether to require_once or require. Default true.
 */
function load_template( $_template_file, $require_once = true ) {
	global $posts, $post, $wp_did_header, $wp_query, $wp_rewrite, $wpdb, $wp_version, $wp, $id, $comment, $user_ID;

	if ( is_array( $wp_query->query_vars ) )
		extract( $wp_query->query_vars, EXTR_SKIP );

	if ( $require_once )
		require_once( $_template_file );
	else
		require( $_template_file );
}