How does the plugin detection and activation code work?

  • Hello fellow coders!

    I’ve always been using WordPress for almost a year now I’ve always been very impressed with the technology behind it. Most impressive imho is the plugin system.

    I’m myself a hobby developer and I’m interested in experimenting with a similar modular /plugin based design. It’s quite easy to make with a database storing information about the modules but then you have to “install” the modules manually to work. What I especially like in wordpress is that it detects the new plugins just by browsing through the plugin folder! That’s some neat stuff.

    Unfortunately I don’t have a clue how that’s done. I’ve been trying to look at wordpress’ source to figure it out but to no good.

    Could someone who actually knows anything about this give me a little heads up? Like how does wordpress read through the files. And how does it read the header’s contents?

    Thanks in advance ??

Viewing 3 replies - 1 through 3 (of 3 total)

  • the simple answer to your question is found by just looking at the function, get_plugins:

    function get_plugins() {
	global $wp_plugins;
if (isset ($wp_plugins)) {
		return $wp_plugins;
	}

	$wp_plugins = array ();
	$plugin_loc = 'wp-content/plugins';
	$plugin_root = ABSPATH.$plugin_loc;

	// Files in wp-content/plugins directory
	$plugins_dir = @ dir($plugin_root);if ($plugins_dir) {
while (($file = $plugins_dir->read()) !== false) {
if (preg_match('|^\.+$|', $file))
continue;
if (is_dir($plugin_root.'/'.$file)) {
$plugins_subdir = @ dir($plugin_root.'/'.$file);
if ($plugins_subdir) {
while (($subfile = $plugins_subdir->read()) !== false) {
if (preg_match('|^\.+$|', $subfile))
continue;
if (preg_match('|\.php$|', $subfile))
$plugin_files[] = "$file/$subfile";
	}
}
} else {
if (preg_match('|\.php$|', $file))
$plugin_files[] = $file;
			}
		}
	}
if ( !$plugins_dir || !$plugin_files )
		return $wp_plugins;
foreach ( $plugin_files as $plugin_file ) {
if ( !is_readable("$plugin_root/$plugin_file"))
continue;
$plugin_data = get_plugin_data("$plugin_root/$plugin_file");

if ( empty ($plugin_data['Name']) )
			continue;
$wp_plugins[plugin_basename($plugin_file)] = $plugin_data;
	}
uasort($wp_plugins, create_function('$a, $b', 'return strnatcasecmp($a["Name"], $b["Name"]);'));
return $wp_plugins;
}

    thats it, thats how it finds ’em.

    the stuff at the top of a plugin is just parsed inside another function:

    function get_plugin_data($plugin_file) {
$plugin_data = implode('', file($plugin_file));
preg_match("|Plugin Name:(.*)|i", $plugin_data, $plugin_name);
preg_match("|Plugin URI:(.*)|i", $plugin_data, $plugin_uri);
preg_match("|Description:(.*)|i", $plugin_data, $description);
preg_match("|Author:(.*)|i", $plugin_data, $author_name);
preg_match("|Author URI:(.*)|i", $plugin_data, $author_uri);
if (preg_match("|Version:(.*)|i", $plugin_data, $version))
$version = trim($version[1]);
else
$version = '';
$description = wptexturize(trim($description[1]));
....
    Thread Starter olmen

    (@olmen)

    Very nice! Thanks a lot! Are these among the admin-functions?

Viewing 3 replies - 1 through 3 (of 3 total)
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