Ticket #49628: 49628.7.diff

src/wp-includes/post.php

@@ -2108 +2108 @@
         /**
          * Filters whether a post type is considered "viewable".
          *
+         * To avoid the potential for type errors in PHP 8.1 or later, this filter
+         * must return a boolean true for the post type to be considered viewable.
+         *
+         * All other values (even truthy values) will result in the function
+         * is_post_type_viewable() returning false.
+         *
          * @since 5.9.0
          *
          * @param bool         $is_viewable Whether the post type is "viewable".
          * @param WP_Post_Type $post_type   Post type object.
          */
-        $is_viewable = apply_filters( 'is_post_type_viewable', $is_viewable, $post_type );
-
-        // Make sure the filtered value is a boolean type before returning it.
-        if ( ! is_bool( $is_viewable ) ) {
-                return false;
-        }
-
-        return $is_viewable;
+        return true === apply_filters( 'is_post_type_viewable', $is_viewable, $post_type );
 }
 
 /**