source: trunk/www.guidonia.net/wp/wp-includes/shortcodes.php@ 44

<?php
/**
 * WordPress API for creating bbcode like tags or what WordPress calls
 * "shortcodes." The tag and attribute parsing or regular expression code is
 * based on the Textpattern tag parser.
 *
 * A few examples are below:
 *
 * [shortcode /]
 * [shortcode foo="bar" baz="bing" /]
 * [shortcode foo="bar"]content[/shortcode]
 *
 * Shortcode tags support attributes and enclosed content, but does not entirely
 * support inline shortcodes in other shortcodes. You will have to call the
 * shortcode parser in your function to account for that.
 *
 * {@internal
 * Please be aware that the above note was made during the beta of WordPress 2.6
 * and in the future may not be accurate. Please update the note when it is no
 * longer the case.}}
 *
 * To apply shortcode tags to content:
 *
 * <code>
 * $out = do_shortcode($content);
 * </code>
 *
 * @link http://codex.wordpress.org/Shortcode_API
 *
 * @package WordPress
 * @subpackage Shortcodes
 * @since 2.5
 */

/**
 * Container for storing shortcode tags and their hook to call for the shortcode
 *
 * @since 2.5
 * @name $shortcode_tags
 * @var array
 * @global array $shortcode_tags
 */
$shortcode_tags = array();

/**
 * Add hook for shortcode tag.
 *
 * There can only be one hook for each shortcode. Which means that if another
 * plugin has a similar shortcode, it will override yours or yours will override
 * theirs depending on which order the plugins are included and/or ran.
 *
 * Simplest example of a shortcode tag using the API:
 *
 * <code>
 * // [footag foo="bar"]
 * function footag_func($atts) {
 *      return "foo = {$atts[foo]}";
 * }
 * add_shortcode('footag', 'footag_func');
 * </code>
 *
 * Example with nice attribute defaults:
 *
 * <code>
 * // [bartag foo="bar"]
 * function bartag_func($atts) {
 *      extract(shortcode_atts(array(
 *              'foo' => 'no foo',
 *              'baz' => 'default baz',
 *      ), $atts));
 *
 *      return "foo = {$foo}";
 * }
 * add_shortcode('bartag', 'bartag_func');
 * </code>
 *
 * Example with enclosed content:
 *
 * <code>
 * // [baztag]content[/baztag]
 * function baztag_func($atts, $content='') {
 *      return "content = $content";
 * }
 * add_shortcode('baztag', 'baztag_func');
 * </code>
 *
 * @since 2.5
 * @uses $shortcode_tags
 *
 * @param string $tag Shortcode tag to be searched in post content.
 * @param callable $func Hook to run when shortcode is found.
 */
function add_shortcode($tag, $func) {
        global $shortcode_tags;

        if ( is_callable($func) )
                $shortcode_tags[$tag] = $func;
}

/**
 * Removes hook for shortcode.
 *
 * @since 2.5
 * @uses $shortcode_tags
 *
 * @param string $tag shortcode tag to remove hook for.
 */
function remove_shortcode($tag) {
        global $shortcode_tags;

        unset($shortcode_tags[$tag]);
}

/**
 * Clear all shortcodes.
 *
 * This function is simple, it clears all of the shortcode tags by replacing the
 * shortcodes global by a empty array. This is actually a very efficient method
 * for removing all shortcodes.
 *
 * @since 2.5
 * @uses $shortcode_tags
 */
function remove_all_shortcodes() {
        global $shortcode_tags;

        $shortcode_tags = array();
}

/**
 * Search content for shortcodes and filter shortcodes through their hooks.
 *
 * If there are no shortcode tags defined, then the content will be returned
 * without any filtering. This might cause issues when plugins are disabled but
 * the shortcode will still show up in the post or content.
 *
 * @since 2.5
 * @uses $shortcode_tags
 * @uses get_shortcode_regex() Gets the search pattern for searching shortcodes.
 *
 * @param string $content Content to search for shortcodes
 * @return string Content with shortcodes filtered out.
 */
function do_shortcode($content) {
        global $shortcode_tags;

        if (empty($shortcode_tags) || !is_array($shortcode_tags))
                return $content;

        $pattern = get_shortcode_regex();
        return preg_replace_callback('/'.$pattern.'/s', 'do_shortcode_tag', $content);
}

/**
 * Retrieve the shortcode regular expression for searching.
 *
 * The regular expression combines the shortcode tags in the regular expression
 * in a regex class.
 *
 * The regular expresion contains 6 different sub matches to help with parsing.
 *
 * 1/6 - An extra [ or ] to allow for escaping shortcodes with double [[]]
 * 2 - The shortcode name
 * 3 - The shortcode argument list
 * 4 - The self closing /
 * 5 - The content of a shortcode when it wraps some content.
 *
 * @since 2.5
 * @uses $shortcode_tags
 *
 * @return string The shortcode search regular expression
 */
function get_shortcode_regex() {
        global $shortcode_tags;
        $tagnames = array_keys($shortcode_tags);
        $tagregexp = join( '|', array_map('preg_quote', $tagnames) );

        return '(.?)\[('.$tagregexp.')\b(.*?)(?:(\/))?\](?:(.+?)\[\/\2\])?(.?)';
}

/**
 * Regular Expression callable for do_shortcode() for calling shortcode hook.
 * @see get_shortcode_regex for details of the match array contents.
 *
 * @since 2.5
 * @access private
 * @uses $shortcode_tags
 *
 * @param array $m Regular expression match array
 * @return mixed False on failure.
 */
function do_shortcode_tag($m) {
        global $shortcode_tags;

        // allow [[foo]] syntax for escaping a tag
        if ($m[1] == '[' && $m[6] == ']') {
                return substr($m[0], 1, -1);
        }

        $tag = $m[2];
        $attr = shortcode_parse_atts($m[3]);

        if ( isset($m[5]) ) {
                // enclosing tag - extra parameter
                return $m[1] . call_user_func($shortcode_tags[$tag], $attr, $m[5], $m[2]) . $m[6];
        } else {
                // self-closing tag
                return $m[1] . call_user_func($shortcode_tags[$tag], $attr, NULL, $m[2]) . $m[6];
        }
}

/**
 * Retrieve all attributes from the shortcodes tag.
 *
 * The attributes list has the attribute name as the key and the value of the
 * attribute as the value in the key/value pair. This allows for easier
 * retrieval of the attributes, since all attributes have to be known.
 *
 * @since 2.5
 *
 * @param string $text
 * @return array List of attributes and their value.
 */
function shortcode_parse_atts($text) {
        $atts = array();
        $pattern = '/(\w+)\s*=\s*"([^"]*)"(?:\s|$)|(\w+)\s*=\s*\'([^\']*)\'(?:\s|$)|(\w+)\s*=\s*([^\s\'"]+)(?:\s|$)|"([^"]*)"(?:\s|$)|(\S+)(?:\s|$)/';
        $text = preg_replace("/[\x{00a0}\x{200b}]+/u", " ", $text);
        if ( preg_match_all($pattern, $text, $match, PREG_SET_ORDER) ) {
                foreach ($match as $m) {
                        if (!empty($m[1]))
                                $atts[strtolower($m[1])] = stripcslashes($m[2]);
                        elseif (!empty($m[3]))
                                $atts[strtolower($m[3])] = stripcslashes($m[4]);
                        elseif (!empty($m[5]))
                                $atts[strtolower($m[5])] = stripcslashes($m[6]);
                        elseif (isset($m[7]) and strlen($m[7]))
                                $atts[] = stripcslashes($m[7]);
                        elseif (isset($m[8]))
                                $atts[] = stripcslashes($m[8]);
                }
        } else {
                $atts = ltrim($text);
        }
        return $atts;
}

/**
 * Combine user attributes with known attributes and fill in defaults when needed.
 *
 * The pairs should be considered to be all of the attributes which are
 * supported by the caller and given as a list. The returned attributes will
 * only contain the attributes in the $pairs list.
 *
 * If the $atts list has unsupported attributes, then they will be ignored and
 * removed from the final returned list.
 *
 * @since 2.5
 *
 * @param array $pairs Entire list of supported attributes and their defaults.
 * @param array $atts User defined attributes in shortcode tag.
 * @return array Combined and filtered attribute list.
 */
function shortcode_atts($pairs, $atts) {
        $atts = (array)$atts;
        $out = array();
        foreach($pairs as $name => $default) {
                if ( array_key_exists($name, $atts) )
                        $out[$name] = $atts[$name];
                else
                        $out[$name] = $default;
        }
        return $out;
}

/**
 * Remove all shortcode tags from the given content.
 *
 * @since 2.5
 * @uses $shortcode_tags
 *
 * @param string $content Content to remove shortcode tags.
 * @return string Content without shortcode tags.
 */
function strip_shortcodes( $content ) {
        global $shortcode_tags;

        if (empty($shortcode_tags) || !is_array($shortcode_tags))
                return $content;

        $pattern = get_shortcode_regex();

        return preg_replace('/'.$pattern.'/s', '', $content);
}

add_filter('the_content', 'do_shortcode', 11); // AFTER wpautop()

?>