$path = dirname( _FILE_ );

$listing = array_filter( scandir( $path ), function( $var ) {

    // remove special directories '.' and '..' from listing
    if ( preg_match( '/^\[.\]{1,2}$/', $var ) ) { return FALSE; }

    // remove files from listing
    if ( !is_dir( $var ) ) { return FALSE; }

    return TRUE;
} );

This is a little snippet of code I've been using a lot recently. This function will return all directories inside the path passed as $path. The functions utilizes the ability of Anonymous Functions, only available in PHP 5.3.0.