Defining symlink compatible paths for WordPress plugins

wp-plugin-path.php

<?php

// include this near the top of your plugin file

$my_plugin_file = __FILE__;

if (isset($plugin)) {
	$my_plugin_file = $plugin;
}
else if (isset($mu_plugin)) {
	$my_plugin_file = $mu_plugin;
}
else if (isset($network_plugin)) {
	$my_plugin_file = $network_plugin;
}

define('MY_PLUGIN_FILE', $my_plugin_file);
define('MY_PLUGIN_PATH', WP_PLUGIN_DIR.'/'.basename(dirname($my_plugin_file)));