Ticket #48249: 48249.2.diff

src/wp-admin/includes/plugin.php

@@ -1373 +1373 @@
         }
 
         $new_sub_menu = array( $menu_title, $capability, $menu_slug, $page_title );
-        if ( null === $position ) {
+        if ( ! is_int( $position ) ) {
+                if ( null !== $position ) {
+                        _doing_it_wrong(
+                                __FUNCTION__,
+                                sprintf(
+                                        /* translators: %s: add_submenu_page() */
+                                        __( 'The seventh parameter passed to %s should be an integer representing menu position.' ),
+                                        '<code>add_submenu_page()</code>'
+                                ),
+                                '5.3.0'
+                        );
+                }
+
                 $submenu[ $parent_slug ][] = $new_sub_menu;
         } else {
                 // If position is equal or higher than the number of items in the array, append the submenu.