WordPress Version: 4.0
/**
* Get the filesystem directory path (with trailing slash) for the plugin __FILE__ passed in.
*
* @since 2.8.0
*
* @param string $file The filename of the plugin (__FILE__).
* @return string the filesystem path of the directory that contains the plugin.
*/
function plugin_dir_path($file)
{
return trailingslashit(dirname($file));
}