WordPress sebagai sebuah platform blogging sudah sangat teruji kehandalannya dalam menangani lebih dari 19 juta blog di wordpress.com dan jutaan blog lainnya yang berbasis WordPress. Sebagai sebuah framework pemrograman, WordPress telah menjadi inspirasi beberapa program lainnya seperti BuddyPress, bbPress, Gravatar, dll. WordPress sendiri sebelum jauh berkembang seperti ini memang diilhami besar oleh sourcecode b2evolution yang kemudian diperas dan dirombak ulang menjadi framework dasar BackPress (http://backpress.org/).

Salah satu fitur unggulan dari platform blogging WordPress adalah kemampuan perluasan yang luar biasa dengan Plugin dan kemampuan handling dengan shortcode, filter, dll. Akan kita bahas tentang API Shortcode WordPress kali ini.

Source code API WordPress bisa anda dapatkan di masing-masing source code blog anda di folder /wp-includes/shortcodes.php. Untuk dapat digunakan diluar platform WordPress, tuju ke baris terakhir file shortcodes.php dan buang source add_filter('the_content', 'do_shortcode', 11); // AFTER wpautop().

Untuk menambahkan shortcode baru dari sebuah fungsi, gunakan pola:
add_shortcode($tag_shortcode,$namafungsi_shortcode);

Fungsi yang diwakili shortcode harus ada (exists).

Selanjutnya siapkan satu buah file PHP, misalnya index.php dan coba serangkaian snippet berikut:

<?php
require 'shortcodes.php'; //ambil dari /wp-includes/shortcodes.php

// untuk shortcode model [footag foo="bar"]
function fungsi_satu($atts) {
	echo "fungsi_satu = {$atts[haha]}";
 }
add_shortcode('fungsisatu', 'fungsi_satu');

// untuk shortcode model [bartag foo="bar"]
function fungsi_dua($atts) {
	extract(shortcode_atts(array(
		'a' => 'variabel a kosong',
		'b' => 'variabel b kosong',
 	), $atts));

	echo "fungsi_dua = {$a}";
}
add_shortcode('fungsidua','fungsi_dua');

// untuk model [baztag]content[/baztag]
function fungsi_tiga($atts, $content='') {
	echo "fungsi_tiga = $content";
}
add_shortcode('fungsitiga', 'fungsi_tiga');

// penggunaan dengan mengeksekusi fungsi do_shortcode($content);
// 1. penggunaan model shortcode pertama
do_shortcode("aku adalah seorang pengembara didunia maya [fungsisatu haha='haha']");

// 2. penggunaan model shortcode dua
do_shortcode("aku adalah seorang pengembara dunia maya [fungsidua a='terserahlah' b]");

// 3. penggunaan model shortcode tiga
do_shortcode("[fungsitiga]aku adalah seorang pengembara dunia maya[/fungsitiga]");

?>

hasil yang akan anda dapatkan dari source diatas adalah:

fungsi_satu = hahafungsi_dua = terserahlahfungsi_tiga = aku adalah seorang pengembara dunia maya

Lampiran (file shortcodes.php):

<?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) );

	// WARNING! Do not change this regex without changing do_shortcode_tag() and strip_shortcodes()
	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], $tag ) . $m[6];
	} else {
		// self-closing tag
		return $m[1] . call_user_func( $shortcode_tags[$tag], $attr, NULL,  $tag ) . $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', '$1$6', $content);
}

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

?>