Ticket #56840: 56840.2.diff

src/wp-includes/class-wp.php

@@ -410 +410 @@
          * @since 2.0.0
          * @since 4.4.0 `X-Pingback` header is added conditionally for single posts that allow pings.
          * @since 6.1.0 Runs after posts have been queried.
+         *
+         * @global WP_Query $wp_query WordPress Query object.
          */
         public function send_headers() {
+                global $wp_query;
+
                 $headers       = array();
                 $status        = null;
                 $exit_required = false;

tests/phpunit/tests/wp/sendHeaders.php

@@ -19 +19 @@
 
                 $this->go_to( home_url() );
         }
+
+        /**
+         * @ticket 56840
+         */
+        public function test_send_headers_sets_x_pingback_for_single_posts_that_allow_pings() {
+                add_action(
+                        'wp_headers',
+                        function ( $headers ) {
+                                $this->assertArrayHasKey( 'X-Pingback', $headers );
+                        }
+                );
+
+                $post_id = self::factory()->post->create();
+                $this->go_to( get_permalink( $post_id ) );
+        }
 }