get_admin_page_parent( $parent = '' )

function get_admin_page_parent( $parent = '' ) {
	global $parent_file, $menu, $submenu, $pagenow, $typenow,
		$plugin_page, $_wp_real_parent_file, $_wp_menu_nopriv, $_wp_submenu_nopriv;

	if ( !empty ( $parent ) && 'admin.php' != $parent ) {
		if ( isset( $_wp_real_parent_file[$parent] ) )
			$parent = $_wp_real_parent_file[$parent];
		return $parent;
	}

	if ( $pagenow == 'admin.php' && isset( $plugin_page ) ) {
		foreach ( (array)$menu as $parent_menu ) {
			if ( $parent_menu[2] == $plugin_page ) {
				$parent_file = $plugin_page;
				if ( isset( $_wp_real_parent_file[$parent_file] ) )
					$parent_file = $_wp_real_parent_file[$parent_file];
				return $parent_file;
			}
		}
		if ( isset( $_wp_menu_nopriv[$plugin_page] ) ) {
			$parent_file = $plugin_page;
			if ( isset( $_wp_real_parent_file[$parent_file] ) )
					$parent_file = $_wp_real_parent_file[$parent_file];
			return $parent_file;
		}
	}

	if ( isset( $plugin_page ) && isset( $_wp_submenu_nopriv[$pagenow][$plugin_page] ) ) {
		$parent_file = $pagenow;
		if ( isset( $_wp_real_parent_file[$parent_file] ) )
			$parent_file = $_wp_real_parent_file[$parent_file];
		return $parent_file;
	}

	foreach (array_keys( (array)$submenu ) as $parent) {
		foreach ( $submenu[$parent] as $submenu_array ) {
			if ( isset( $_wp_real_parent_file[$parent] ) )
				$parent = $_wp_real_parent_file[$parent];
			if ( !empty($typenow) && ($submenu_array[2] == "$pagenow?post_type=$typenow") ) {
				$parent_file = $parent;
				return $parent;
			} elseif ( $submenu_array[2] == $pagenow && empty($typenow) && ( empty($parent_file) || false === strpos($parent_file, '?') ) ) {
				$parent_file = $parent;
				return $parent;
			} elseif ( isset( $plugin_page ) && ($plugin_page == $submenu_array[2] ) ) {
				$parent_file = $parent;
				return $parent;
			}
		}
	}

	if ( empty($parent_file) )
		$parent_file = '';
	return '';
}