get_admin_page_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 ( 'admin.php' === $pagenow && 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( $typenow ) && ( "$pagenow?post_type=$typenow" === $submenu_array[2] ) ) {
				$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 '';
}