From 71cb111109adb29ace47747634e4532433fea502 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B6ren=20W=C3=BCnsch?= <soeren.wrede@parshipgroup.com>
Date: Thu, 6 Aug 2026 15:02:24 +0200
Subject: [PATCH] Code Quality: Use the null coalescing assignment operator for
 array initialization. Replace `if ( ! isset( $x ) ) { $x = array(); }` with
 `$x ??= array();`, using the null coalescing assignment operator introduced
 in PHP 7.4.

---
 src/wp-admin/includes/dashboard.php           |  4 +--
 src/wp-admin/includes/nav-menu.php            |  4 +--
 src/wp-admin/includes/post.php                |  4 +--
 src/wp-admin/includes/template.php            | 28 +++++--------------
 src/wp-admin/includes/widgets.php             |  4 +--
 src/wp-includes/block-supports/anchor.php     |  4 +--
 src/wp-includes/block-template-utils.php      |  4 +--
 src/wp-includes/blocks.php                    | 12 ++------
 src/wp-includes/capabilities.php              |  8 ++----
 .../class-wp-block-styles-registry.php        |  4 +--
 .../class-wp-customize-manager.php            | 16 +++--------
 .../class-wp-customize-nav-menus.php          |  4 +--
 .../class-wp-customize-setting.php            |  8 ++----
 .../class-wp-customize-widgets.php            | 10 ++-----
 src/wp-includes/class-wp-duotone.php          |  4 +--
 .../class-wp-metadata-lazyloader.php          |  4 +--
 src/wp-includes/class-wp-query.php            | 10 ++-----
 .../class-wp-speculation-rules.php            |  4 +--
 src/wp-includes/class-wp-tax-query.php        |  6 ++--
 src/wp-includes/class-wp-theme-json.php       |  4 +--
 src/wp-includes/class-wp-theme.php            |  6 ++--
 src/wp-includes/class-wp-token-map.php        |  4 +--
 ...ass-wp-customize-nav-menu-item-setting.php |  4 +--
 .../class-wp-customize-nav-menu-setting.php   | 14 +++-------
 ...class-wp-widget-form-customize-control.php |  6 ++--
 src/wp-includes/general-template.php          |  4 +--
 .../class-wp-interactivity-api.php            | 12 ++------
 .../l10n/class-wp-translation-controller.php  |  4 +--
 src/wp-includes/meta.php                      |  6 ++--
 src/wp-includes/plugin.php                    | 12 ++------
 .../rest-api/class-wp-rest-request.php        |  4 +--
 .../rest-api/class-wp-rest-server.php         |  4 +--
 .../class-wp-rest-attachments-controller.php  |  4 +--
 .../class-wp-rest-menus-controller.php        |  4 +--
 src/wp-includes/taxonomy.php                  | 20 ++++---------
 35 files changed, 69 insertions(+), 185 deletions(-)

diff --git a/src/wp-admin/includes/dashboard.php b/src/wp-admin/includes/dashboard.php
index 0fe5c62064b64..cfed8f0a064c2 100644
--- a/src/wp-admin/includes/dashboard.php
+++ b/src/wp-admin/includes/dashboard.php
@@ -1274,9 +1274,7 @@ function wp_dashboard_rss_control( $widget_id, $form_inputs = array() ) {
 		$widget_options = array();
 	}
 
-	if ( ! isset( $widget_options[ $widget_id ] ) ) {
-		$widget_options[ $widget_id ] = array();
-	}
+	$widget_options[ $widget_id ] ??= array();
 
 	$number = 1; // Hack to use wp_widget_rss_form().
 
diff --git a/src/wp-admin/includes/nav-menu.php b/src/wp-admin/includes/nav-menu.php
index f26d63d528e78..dc90feb3b3309 100644
--- a/src/wp-admin/includes/nav-menu.php
+++ b/src/wp-admin/includes/nav-menu.php
@@ -1483,9 +1483,7 @@ function wp_nav_menu_update_menu_items( $nav_menu_selected_id, $nav_menu_selecte
 	$auto_add        = ! empty( $_POST['auto-add-pages'] );
 	$nav_menu_option = (array) get_option( 'nav_menu_options' );
 
-	if ( ! isset( $nav_menu_option['auto_add'] ) ) {
-		$nav_menu_option['auto_add'] = array();
-	}
+	$nav_menu_option['auto_add'] ??= array();
 
 	if ( $auto_add ) {
 		if ( ! in_array( $nav_menu_selected_id, $nav_menu_option['auto_add'], true ) ) {
diff --git a/src/wp-admin/includes/post.php b/src/wp-admin/includes/post.php
index 39d267b623037..9b60abf886ab4 100644
--- a/src/wp-admin/includes/post.php
+++ b/src/wp-admin/includes/post.php
@@ -2335,9 +2335,7 @@ function get_block_editor_server_block_settings() {
 				continue;
 			}
 
-			if ( ! isset( $blocks[ $block_name ] ) ) {
-				$blocks[ $block_name ] = array();
-			}
+			$blocks[ $block_name ] ??= array();
 
 			$blocks[ $block_name ][ $key ] = $block_type->{ $field };
 		}
diff --git a/src/wp-admin/includes/template.php b/src/wp-admin/includes/template.php
index 418bfd7def697..2d29418322c94 100644
--- a/src/wp-admin/includes/template.php
+++ b/src/wp-admin/includes/template.php
@@ -1098,15 +1098,9 @@ function add_meta_box( $id, $title, $callback, $screen = null, $context = 'advan
 
 	$page = $screen->id;
 
-	if ( ! isset( $wp_meta_boxes ) ) {
-		$wp_meta_boxes = array();
-	}
-	if ( ! isset( $wp_meta_boxes[ $page ] ) ) {
-		$wp_meta_boxes[ $page ] = array();
-	}
-	if ( ! isset( $wp_meta_boxes[ $page ][ $context ] ) ) {
-		$wp_meta_boxes[ $page ][ $context ] = array();
-	}
+	$wp_meta_boxes                      ??= array();
+	$wp_meta_boxes[ $page ]             ??= array();
+	$wp_meta_boxes[ $page ][ $context ] ??= array();
 
 	foreach ( array_keys( $wp_meta_boxes[ $page ] ) as $a_context ) {
 		foreach ( array( 'high', 'core', 'default', 'low' ) as $a_priority ) {
@@ -1158,9 +1152,7 @@ function add_meta_box( $id, $title, $callback, $screen = null, $context = 'advan
 		$priority = 'low';
 	}
 
-	if ( ! isset( $wp_meta_boxes[ $page ][ $context ][ $priority ] ) ) {
-		$wp_meta_boxes[ $page ][ $context ][ $priority ] = array();
-	}
+	$wp_meta_boxes[ $page ][ $context ][ $priority ] ??= array();
 
 	$wp_meta_boxes[ $page ][ $context ][ $priority ][ $id ] = array(
 		'id'       => $id,
@@ -1502,15 +1494,9 @@ function remove_meta_box( $id, $screen, $context ) {
 
 	$page = $screen->id;
 
-	if ( ! isset( $wp_meta_boxes ) ) {
-		$wp_meta_boxes = array();
-	}
-	if ( ! isset( $wp_meta_boxes[ $page ] ) ) {
-		$wp_meta_boxes[ $page ] = array();
-	}
-	if ( ! isset( $wp_meta_boxes[ $page ][ $context ] ) ) {
-		$wp_meta_boxes[ $page ][ $context ] = array();
-	}
+	$wp_meta_boxes                      ??= array();
+	$wp_meta_boxes[ $page ]             ??= array();
+	$wp_meta_boxes[ $page ][ $context ] ??= array();
 
 	foreach ( array( 'high', 'core', 'default', 'low' ) as $priority ) {
 		$wp_meta_boxes[ $page ][ $context ][ $priority ][ $id ] = false;
diff --git a/src/wp-admin/includes/widgets.php b/src/wp-admin/includes/widgets.php
index e751602866b0d..c4510931411c8 100644
--- a/src/wp-admin/includes/widgets.php
+++ b/src/wp-admin/includes/widgets.php
@@ -29,9 +29,7 @@ function wp_list_widgets() {
 		$sidebar = is_active_widget( $widget['callback'], $widget['id'], false, false );
 		$done[]  = $widget['callback'];
 
-		if ( ! isset( $widget['params'][0] ) ) {
-			$widget['params'][0] = array();
-		}
+		$widget['params'][0] ??= array();
 
 		$args = array(
 			'widget_id'   => $widget['id'],
diff --git a/src/wp-includes/block-supports/anchor.php b/src/wp-includes/block-supports/anchor.php
index 657234f8cbf6c..c6eceea13669c 100644
--- a/src/wp-includes/block-supports/anchor.php
+++ b/src/wp-includes/block-supports/anchor.php
@@ -19,9 +19,7 @@ function wp_register_anchor_support( WP_Block_Type $block_type ) {
 		return;
 	}
 
-	if ( ! isset( $block_type->attributes ) ) {
-		$block_type->attributes = array();
-	}
+	$block_type->attributes ??= array();
 
 	if ( ! array_key_exists( 'anchor', $block_type->attributes ) ) {
 		$block_type->attributes['anchor'] = array(
diff --git a/src/wp-includes/block-template-utils.php b/src/wp-includes/block-template-utils.php
index a7d5d4aa1141d..843aa55ce431e 100644
--- a/src/wp-includes/block-template-utils.php
+++ b/src/wp-includes/block-template-utils.php
@@ -1783,9 +1783,7 @@ function inject_ignored_hooked_blocks_metadata_attributes( $changes, $deprecated
 		$wrapper_block         = parse_blocks( $wrapper_block_markup )[0];
 		$ignored_hooked_blocks = $wrapper_block['attrs']['metadata']['ignoredHookedBlocks'] ?? array();
 		if ( ! empty( $ignored_hooked_blocks ) ) {
-			if ( ! isset( $changes->meta_input ) ) {
-				$changes->meta_input = array();
-			}
+			$changes->meta_input                            ??= array();
 			$changes->meta_input['_wp_ignored_hooked_blocks'] = wp_json_encode( $ignored_hooked_blocks );
 		}
 	} else {
diff --git a/src/wp-includes/blocks.php b/src/wp-includes/blocks.php
index a0360ffdc8bf8..89d47891af435 100644
--- a/src/wp-includes/blocks.php
+++ b/src/wp-includes/blocks.php
@@ -979,12 +979,8 @@ function get_hooked_blocks() {
 			continue;
 		}
 		foreach ( $block_type->block_hooks as $anchor_block_type => $relative_position ) {
-			if ( ! isset( $hooked_blocks[ $anchor_block_type ] ) ) {
-				$hooked_blocks[ $anchor_block_type ] = array();
-			}
-			if ( ! isset( $hooked_blocks[ $anchor_block_type ][ $relative_position ] ) ) {
-				$hooked_blocks[ $anchor_block_type ][ $relative_position ] = array();
-			}
+			$hooked_blocks[ $anchor_block_type ]                       ??= array();
+			$hooked_blocks[ $anchor_block_type ][ $relative_position ] ??= array();
 			$hooked_blocks[ $anchor_block_type ][ $relative_position ][] = $block_type->name;
 		}
 	}
@@ -1490,9 +1486,7 @@ function update_ignored_hooked_blocks_postmeta( $post ) {
 			$ignored_hooked_blocks          = array_unique( array_merge( $ignored_hooked_blocks, $existing_ignored_hooked_blocks ) );
 		}
 
-		if ( ! isset( $post->meta_input ) ) {
-			$post->meta_input = array();
-		}
+		$post->meta_input                            ??= array();
 		$post->meta_input['_wp_ignored_hooked_blocks'] = json_encode( $ignored_hooked_blocks );
 	}
 
diff --git a/src/wp-includes/capabilities.php b/src/wp-includes/capabilities.php
index 645ab5588ee5e..3d92ee7357bbc 100644
--- a/src/wp-includes/capabilities.php
+++ b/src/wp-includes/capabilities.php
@@ -830,11 +830,9 @@ function map_meta_cap( $cap, $user_id, ...$args ) {
 			}
 			$post_type_object = get_post_type_object( $object_subtype );
 			// Initialize empty array if it doesn't exist.
-			if ( ! isset( $post_type_object->capabilities ) ) {
-				$post_type_object->capabilities = array();
-			}
-			$post_type_capabilities = get_post_type_capabilities( $post_type_object );
-			$caps                   = map_meta_cap( $post_type_capabilities->edit_post, $user_id, $object_id );
+			$post_type_object->capabilities ??= array();
+			$post_type_capabilities           = get_post_type_capabilities( $post_type_object );
+			$caps                             = map_meta_cap( $post_type_capabilities->edit_post, $user_id, $object_id );
 			break;
 		default:
 			// Handle meta capabilities for custom post types.
diff --git a/src/wp-includes/class-wp-block-styles-registry.php b/src/wp-includes/class-wp-block-styles-registry.php
index 9efdb30157235..78c4b56701824 100644
--- a/src/wp-includes/class-wp-block-styles-registry.php
+++ b/src/wp-includes/class-wp-block-styles-registry.php
@@ -99,9 +99,7 @@ public function register( $block_name, $style_properties ) {
 		}
 
 		foreach ( $block_names as $name ) {
-			if ( ! isset( $this->registered_block_styles[ $name ] ) ) {
-				$this->registered_block_styles[ $name ] = array();
-			}
+			$this->registered_block_styles[ $name ]                    ??= array();
 			$this->registered_block_styles[ $name ][ $block_style_name ] = $style_properties;
 		}
 
diff --git a/src/wp-includes/class-wp-customize-manager.php b/src/wp-includes/class-wp-customize-manager.php
index e298b04efcf90..df07511b8dd8e 100644
--- a/src/wp-includes/class-wp-customize-manager.php
+++ b/src/wp-includes/class-wp-customize-manager.php
@@ -2817,9 +2817,7 @@ public function save_changeset_post( $args = array() ) {
 
 		// Ensure that all post values are included in the changeset data.
 		foreach ( $post_values as $setting_id => $post_value ) {
-			if ( ! isset( $args['data'][ $setting_id ] ) ) {
-				$args['data'][ $setting_id ] = array();
-			}
+			$args['data'][ $setting_id ] ??= array();
 			if ( ! isset( $args['data'][ $setting_id ]['value'] ) ) {
 				$args['data'][ $setting_id ]['value'] = $post_value;
 			}
@@ -2846,9 +2844,7 @@ public function save_changeset_post( $args = array() ) {
 				unset( $data[ $changeset_setting_id ] );
 			} else {
 
-				if ( ! isset( $data[ $changeset_setting_id ] ) ) {
-					$data[ $changeset_setting_id ] = array();
-				}
+				$data[ $changeset_setting_id ] ??= array();
 
 				// Merge any additional setting params that have been supplied with the existing params.
 				$merged_setting_params = array_merge( $data[ $changeset_setting_id ], $setting_params );
@@ -3516,9 +3512,7 @@ public function _publish_changeset_values( $changeset_post_id ) {
 				preg_match( $namespace_pattern, $raw_setting_id, $matches )
 			);
 			if ( $is_theme_mod_setting ) {
-				if ( ! isset( $theme_mod_settings[ $matches['stylesheet'] ] ) ) {
-					$theme_mod_settings[ $matches['stylesheet'] ] = array();
-				}
+				$theme_mod_settings[ $matches['stylesheet'] ]                         ??= array();
 				$theme_mod_settings[ $matches['stylesheet'] ][ $matches['setting_id'] ] = $setting_params;
 
 				if ( $this->get_stylesheet() === $matches['stylesheet'] ) {
@@ -3665,9 +3659,7 @@ protected function update_stashed_theme_mod_settings( $inactive_theme_mod_settin
 
 		// Merge inactive theme mods with the stashed theme mod settings.
 		foreach ( $inactive_theme_mod_settings as $stylesheet => $theme_mod_settings ) {
-			if ( ! isset( $stashed_theme_mod_settings[ $stylesheet ] ) ) {
-				$stashed_theme_mod_settings[ $stylesheet ] = array();
-			}
+			$stashed_theme_mod_settings[ $stylesheet ] ??= array();
 
 			$stashed_theme_mod_settings[ $stylesheet ] = array_merge(
 				$stashed_theme_mod_settings[ $stylesheet ],
diff --git a/src/wp-includes/class-wp-customize-nav-menus.php b/src/wp-includes/class-wp-customize-nav-menus.php
index 07b2742264775..3f58dfb71a093 100644
--- a/src/wp-includes/class-wp-customize-nav-menus.php
+++ b/src/wp-includes/class-wp-customize-nav-menus.php
@@ -977,9 +977,7 @@ public function insert_auto_draft_post( $postarr ) {
 		if ( empty( $postarr['post_name'] ) ) {
 			$postarr['post_name'] = sanitize_title( $postarr['post_title'] );
 		}
-		if ( ! isset( $postarr['meta_input'] ) ) {
-			$postarr['meta_input'] = array();
-		}
+		$postarr['meta_input']                             ??= array();
 		$postarr['meta_input']['_customize_draft_post_name'] = $postarr['post_name'];
 		$postarr['meta_input']['_customize_changeset_uuid']  = $this->manager->changeset_uuid();
 		unset( $postarr['post_name'] );
diff --git a/src/wp-includes/class-wp-customize-setting.php b/src/wp-includes/class-wp-customize-setting.php
index 2586646f7f2e1..7fa1f886a4184 100644
--- a/src/wp-includes/class-wp-customize-setting.php
+++ b/src/wp-includes/class-wp-customize-setting.php
@@ -248,9 +248,7 @@ final public function id_data() {
 	 */
 	protected function aggregate_multidimensional() {
 		$id_base = $this->id_data['base'];
-		if ( ! isset( self::$aggregated_multidimensionals[ $this->type ] ) ) {
-			self::$aggregated_multidimensionals[ $this->type ] = array();
-		}
+		self::$aggregated_multidimensionals[ $this->type ] ??= array();
 		if ( ! isset( self::$aggregated_multidimensionals[ $this->type ][ $id_base ] ) ) {
 			self::$aggregated_multidimensionals[ $this->type ][ $id_base ] = array(
 				'previewed_instances'       => array(), // Calling preview() will add the $setting to the array.
@@ -887,9 +885,7 @@ final protected function multidimensional( &$root, $keys, $create = false ) {
 				// Account for an array overriding a string or object value.
 				$node = array();
 			}
-			if ( ! isset( $node[ $last ] ) ) {
-				$node[ $last ] = array();
-			}
+			$node[ $last ] ??= array();
 		}
 
 		if ( ! isset( $node[ $last ] ) ) {
diff --git a/src/wp-includes/class-wp-customize-widgets.php b/src/wp-includes/class-wp-customize-widgets.php
index 7484d2deee7da..2f1b4193d8e24 100644
--- a/src/wp-includes/class-wp-customize-widgets.php
+++ b/src/wp-includes/class-wp-customize-widgets.php
@@ -1080,9 +1080,7 @@ public function get_available_widgets() {
 			$sidebar = is_active_widget( $widget['callback'], $widget['id'], false, false );
 			$done[]  = $widget['callback'];
 
-			if ( ! isset( $widget['params'][0] ) ) {
-				$widget['params'][0] = array();
-			}
+			$widget['params'][0] ??= array();
 
 			$available_widget = $widget;
 			unset( $available_widget['callback'] ); // Not serializable to JSON.
@@ -1885,10 +1883,8 @@ public function filter_dynamic_sidebar_params( $params ) {
 	 */
 	public function filter_wp_kses_allowed_data_attributes( $allowed_html ) {
 		foreach ( array_keys( $this->before_widget_tags_seen ) as $tag_name ) {
-			if ( ! isset( $allowed_html[ $tag_name ] ) ) {
-				$allowed_html[ $tag_name ] = array();
-			}
-			$allowed_html[ $tag_name ] = array_merge(
+			$allowed_html[ $tag_name ] ??= array();
+			$allowed_html[ $tag_name ]   = array_merge(
 				$allowed_html[ $tag_name ],
 				array_fill_keys(
 					array(
diff --git a/src/wp-includes/class-wp-duotone.php b/src/wp-includes/class-wp-duotone.php
index 0e12e7ca7f306..53b8fe4353f07 100644
--- a/src/wp-includes/class-wp-duotone.php
+++ b/src/wp-includes/class-wp-duotone.php
@@ -1276,9 +1276,7 @@ public static function output_footer_assets() {
 	public static function add_editor_settings( $settings ) {
 		$global_styles_presets = self::get_all_global_styles_presets();
 		if ( ! empty( $global_styles_presets ) ) {
-			if ( ! isset( $settings['styles'] ) ) {
-				$settings['styles'] = array();
-			}
+			$settings['styles'] ??= array();
 
 			$settings['styles'][] = array(
 				// For the editor we can add all of the presets by default.
diff --git a/src/wp-includes/class-wp-metadata-lazyloader.php b/src/wp-includes/class-wp-metadata-lazyloader.php
index f9c02391d2b1d..0bae09debe810 100644
--- a/src/wp-includes/class-wp-metadata-lazyloader.php
+++ b/src/wp-includes/class-wp-metadata-lazyloader.php
@@ -84,9 +84,7 @@ public function queue_objects( $object_type, $object_ids ) {
 
 		$type_settings = $this->settings[ $object_type ];
 
-		if ( ! isset( $this->pending_objects[ $object_type ] ) ) {
-			$this->pending_objects[ $object_type ] = array();
-		}
+		$this->pending_objects[ $object_type ] ??= array();
 
 		foreach ( $object_ids as $object_id ) {
 			// Keyed by ID for faster lookup.
diff --git a/src/wp-includes/class-wp-query.php b/src/wp-includes/class-wp-query.php
index 228691d26d12b..aad2fbc7af23c 100644
--- a/src/wp-includes/class-wp-query.php
+++ b/src/wp-includes/class-wp-query.php
@@ -643,9 +643,7 @@ public function fill_query_vars( $query_vars ) {
 		);
 
 		foreach ( $array_keys as $key ) {
-			if ( ! isset( $query_vars[ $key ] ) ) {
-				$query_vars[ $key ] = array();
-			}
+			$query_vars[ $key ] ??= array();
 		}
 
 		return $query_vars;
@@ -1279,10 +1277,8 @@ public function parse_tax_query( &$query_vars ) {
 		}
 
 		if ( ! empty( $query_vars['category__and'] ) && 1 === count( (array) $query_vars['category__and'] ) ) {
-			$query_vars['category__and'] = (array) $query_vars['category__and'];
-			if ( ! isset( $query_vars['category__in'] ) ) {
-				$query_vars['category__in'] = array();
-			}
+			$query_vars['category__and']  = (array) $query_vars['category__and'];
+			$query_vars['category__in'] ??= array();
 			$query_vars['category__in'][] = absint( reset( $query_vars['category__and'] ) );
 			unset( $query_vars['category__and'] );
 		}
diff --git a/src/wp-includes/class-wp-speculation-rules.php b/src/wp-includes/class-wp-speculation-rules.php
index 45e6f3ff0be0a..11794c83b8717 100644
--- a/src/wp-includes/class-wp-speculation-rules.php
+++ b/src/wp-includes/class-wp-speculation-rules.php
@@ -204,9 +204,7 @@ public function add_rule( string $mode, string $id, array $rule ): bool {
 			}
 		}
 
-		if ( ! isset( $this->rules_by_mode[ $mode ] ) ) {
-			$this->rules_by_mode[ $mode ] = array();
-		}
+		$this->rules_by_mode[ $mode ] ??= array();
 
 		$this->rules_by_mode[ $mode ][ $id ] = $rule;
 		return true;
diff --git a/src/wp-includes/class-wp-tax-query.php b/src/wp-includes/class-wp-tax-query.php
index c6ec3258cc201..9229dcce8fb82 100644
--- a/src/wp-includes/class-wp-tax-query.php
+++ b/src/wp-includes/class-wp-tax-query.php
@@ -160,10 +160,8 @@ public function sanitize_query( $queries ) {
 				 * $queried_terms array, for use in WP_Query.
 				 */
 				if ( ! empty( $cleaned_clause['taxonomy'] ) && 'NOT IN' !== $cleaned_clause['operator'] ) {
-					$taxonomy = $cleaned_clause['taxonomy'];
-					if ( ! isset( $this->queried_terms[ $taxonomy ] ) ) {
-						$this->queried_terms[ $taxonomy ] = array();
-					}
+					$taxonomy                           = $cleaned_clause['taxonomy'];
+					$this->queried_terms[ $taxonomy ] ??= array();
 
 					/*
 					 * Backward compatibility: Only store the first
diff --git a/src/wp-includes/class-wp-theme-json.php b/src/wp-includes/class-wp-theme-json.php
index 7e2cb54731b1f..39ac5ec48b052 100644
--- a/src/wp-includes/class-wp-theme-json.php
+++ b/src/wp-includes/class-wp-theme-json.php
@@ -2511,9 +2511,7 @@ protected function get_css_variables( $nodes, $origins ) {
 
 				$target = static::get_feature_selector( $feature_selectors, $preset_metadata['path'][0], $selector );
 
-				if ( ! isset( $vars_by_selector[ $target ] ) ) {
-					$vars_by_selector[ $target ] = array();
-				}
+				$vars_by_selector[ $target ] ??= array();
 
 				foreach ( $values_by_slug as $slug => $value ) {
 					$vars_by_selector[ $target ][] = array(
diff --git a/src/wp-includes/class-wp-theme.php b/src/wp-includes/class-wp-theme.php
index 6a18e7a534daa..4284a589ed3da 100644
--- a/src/wp-includes/class-wp-theme.php
+++ b/src/wp-includes/class-wp-theme.php
@@ -1357,10 +1357,8 @@ public function get_post_templates() {
 				}
 
 				foreach ( $types as $type ) {
-					$type = sanitize_key( $type );
-					if ( ! isset( $post_templates[ $type ] ) ) {
-						$post_templates[ $type ] = array();
-					}
+					$type                      = sanitize_key( $type );
+					$post_templates[ $type ] ??= array();
 
 					$post_templates[ $type ][ $file ] = $headers['TemplateName'];
 				}
diff --git a/src/wp-includes/class-wp-token-map.php b/src/wp-includes/class-wp-token-map.php
index fc223b187f8c5..93f47845b02c5 100644
--- a/src/wp-includes/class-wp-token-map.php
+++ b/src/wp-includes/class-wp-token-map.php
@@ -312,9 +312,7 @@ public static function from_array( array $mappings, int $key_length = 2 ): ?WP_T
 			} else {
 				$group = substr( $word, 0, $key_length );
 
-				if ( ! isset( $groups[ $group ] ) ) {
-					$groups[ $group ] = array();
-				}
+				$groups[ $group ] ??= array();
 
 				$groups[ $group ][] = array( substr( $word, $key_length ), $mapping );
 			}
diff --git a/src/wp-includes/customize/class-wp-customize-nav-menu-item-setting.php b/src/wp-includes/customize/class-wp-customize-nav-menu-item-setting.php
index aca7619a6b895..de6c6a1fe13ef 100644
--- a/src/wp-includes/customize/class-wp-customize-nav-menu-item-setting.php
+++ b/src/wp-includes/customize/class-wp-customize-nav-menu-item-setting.php
@@ -902,9 +902,7 @@ protected function update( $value ) {
 	 * @return array Save response data.
 	 */
 	public function amend_customize_save_response( $data ) {
-		if ( ! isset( $data['nav_menu_item_updates'] ) ) {
-			$data['nav_menu_item_updates'] = array();
-		}
+		$data['nav_menu_item_updates'] ??= array();
 
 		$data['nav_menu_item_updates'][] = array(
 			'post_id'          => $this->post_id,
diff --git a/src/wp-includes/customize/class-wp-customize-nav-menu-setting.php b/src/wp-includes/customize/class-wp-customize-nav-menu-setting.php
index 138ab8806e719..83489d21cf460 100644
--- a/src/wp-includes/customize/class-wp-customize-nav-menu-setting.php
+++ b/src/wp-includes/customize/class-wp-customize-nav-menu-setting.php
@@ -601,10 +601,8 @@ protected function update( $value ) {
 	 * @return array (Maybe) modified nav_menu_options array.
 	 */
 	protected function filter_nav_menu_options_value( $nav_menu_options, $menu_id, $auto_add ) {
-		$nav_menu_options = (array) $nav_menu_options;
-		if ( ! isset( $nav_menu_options['auto_add'] ) ) {
-			$nav_menu_options['auto_add'] = array();
-		}
+		$nav_menu_options               = (array) $nav_menu_options;
+		$nav_menu_options['auto_add'] ??= array();
 
 		$i = array_search( $menu_id, $nav_menu_options['auto_add'], true );
 
@@ -628,12 +626,8 @@ protected function filter_nav_menu_options_value( $nav_menu_options, $menu_id, $
 	 * @return array Export data.
 	 */
 	public function amend_customize_save_response( $data ) {
-		if ( ! isset( $data['nav_menu_updates'] ) ) {
-			$data['nav_menu_updates'] = array();
-		}
-		if ( ! isset( $data['widget_nav_menu_updates'] ) ) {
-			$data['widget_nav_menu_updates'] = array();
-		}
+		$data['nav_menu_updates']        ??= array();
+		$data['widget_nav_menu_updates'] ??= array();
 
 		$data['nav_menu_updates'][] = array(
 			'term_id'          => $this->term_id,
diff --git a/src/wp-includes/customize/class-wp-widget-form-customize-control.php b/src/wp-includes/customize/class-wp-widget-form-customize-control.php
index cfab1886062fd..3ac0e69969ed5 100644
--- a/src/wp-includes/customize/class-wp-widget-form-customize-control.php
+++ b/src/wp-includes/customize/class-wp-widget-form-customize-control.php
@@ -98,10 +98,8 @@ public function to_json() {
 		// Get the widget_control and widget_content.
 		require_once ABSPATH . 'wp-admin/includes/widgets.php';
 
-		$widget = $wp_registered_widgets[ $this->widget_id ];
-		if ( ! isset( $widget['params'][0] ) ) {
-			$widget['params'][0] = array();
-		}
+		$widget                = $wp_registered_widgets[ $this->widget_id ];
+		$widget['params'][0] ??= array();
 
 		$args = array(
 			'widget_id'   => $widget['id'],
diff --git a/src/wp-includes/general-template.php b/src/wp-includes/general-template.php
index 22a1d3e307d3e..c59100e42cd6f 100644
--- a/src/wp-includes/general-template.php
+++ b/src/wp-includes/general-template.php
@@ -5095,9 +5095,7 @@ function paginate_links( $args = '' ) {
 function wp_admin_css_color( $key, $name, $url, $colors = array(), $icons = array() ) {
 	global $_wp_admin_css_colors;
 
-	if ( ! isset( $_wp_admin_css_colors ) ) {
-		$_wp_admin_css_colors = array();
-	}
+	$_wp_admin_css_colors ??= array();
 
 	$_wp_admin_css_colors[ $key ] = (object) array(
 		'name'        => $name,
diff --git a/src/wp-includes/interactivity-api/class-wp-interactivity-api.php b/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
index 62bfc29cfc03f..ecd8b1e9b085e 100644
--- a/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
+++ b/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
@@ -192,9 +192,7 @@ public function state( ?string $store_namespace = null, ?array $state = null ):
 
 			$store_namespace = end( $this->namespace_stack );
 		}
-		if ( ! isset( $this->state_data[ $store_namespace ] ) ) {
-			$this->state_data[ $store_namespace ] = array();
-		}
+		$this->state_data[ $store_namespace ] ??= array();
 		if ( is_array( $state ) ) {
 			$this->state_data[ $store_namespace ] = array_replace_recursive(
 				$this->state_data[ $store_namespace ],
@@ -220,9 +218,7 @@ public function state( ?string $store_namespace = null, ?array $state = null ):
 	 *               $config argument was provided.
 	 */
 	public function config( string $store_namespace, array $config = array() ): array {
-		if ( ! isset( $this->config_data[ $store_namespace ] ) ) {
-			$this->config_data[ $store_namespace ] = array();
-		}
+		$this->config_data[ $store_namespace ] ??= array();
 		if ( is_array( $config ) ) {
 			$this->config_data[ $store_namespace ] = array_replace_recursive(
 				$this->config_data[ $store_namespace ],
@@ -260,9 +256,7 @@ public function print_client_interactivity_data() {
 	 * @return array Data for the Interactivity Router script module.
 	 */
 	public function filter_script_module_interactivity_router_data( array $data ): array {
-		if ( ! isset( $data['i18n'] ) ) {
-			$data['i18n'] = array();
-		}
+		$data['i18n']          ??= array();
 		$data['i18n']['loading'] = __( 'Loading page, please wait.' );
 		$data['i18n']['loaded']  = __( 'Page Loaded.' );
 		return $data;
diff --git a/src/wp-includes/l10n/class-wp-translation-controller.php b/src/wp-includes/l10n/class-wp-translation-controller.php
index c68cf32add6d6..da7a35203aa80 100644
--- a/src/wp-includes/l10n/class-wp-translation-controller.php
+++ b/src/wp-includes/l10n/class-wp-translation-controller.php
@@ -134,9 +134,7 @@ public function load_file( string $translation_file, string $textdomain = 'defau
 			return false;
 		}
 
-		if ( ! isset( $this->loaded_translations[ $locale ][ $textdomain ] ) ) {
-			$this->loaded_translations[ $locale ][ $textdomain ] = array();
-		}
+		$this->loaded_translations[ $locale ][ $textdomain ] ??= array();
 
 		$this->loaded_translations[ $locale ][ $textdomain ][] = $moe;
 
diff --git a/src/wp-includes/meta.php b/src/wp-includes/meta.php
index c657c6c2e7af3..874604129832f 100644
--- a/src/wp-includes/meta.php
+++ b/src/wp-includes/meta.php
@@ -1224,10 +1224,8 @@ function update_meta_cache( $meta_type, $object_ids ) {
 
 	$data = array();
 	foreach ( $non_cached_ids as $id ) {
-		if ( ! isset( $cache[ $id ] ) ) {
-			$cache[ $id ] = array();
-		}
-		$data[ $id ] = $cache[ $id ];
+		$cache[ $id ] ??= array();
+		$data[ $id ]    = $cache[ $id ];
 	}
 	wp_cache_add_multiple( $data, $cache_group );
 
diff --git a/src/wp-includes/plugin.php b/src/wp-includes/plugin.php
index f64b584374c8e..5770a2ded7c2a 100644
--- a/src/wp-includes/plugin.php
+++ b/src/wp-includes/plugin.php
@@ -43,17 +43,11 @@
 	$wp_filter = array();
 }
 
-if ( ! isset( $wp_actions ) ) {
-	$wp_actions = array();
-}
+$wp_actions ??= array();
 
-if ( ! isset( $wp_filters ) ) {
-	$wp_filters = array();
-}
+$wp_filters ??= array();
 
-if ( ! isset( $wp_current_filter ) ) {
-	$wp_current_filter = array();
-}
+$wp_current_filter ??= array();
 
 /**
  * Adds a callback function to a filter hook.
diff --git a/src/wp-includes/rest-api/class-wp-rest-request.php b/src/wp-includes/rest-api/class-wp-rest-request.php
index a6169ada2c05b..a2606e1a46dff 100644
--- a/src/wp-includes/rest-api/class-wp-rest-request.php
+++ b/src/wp-includes/rest-api/class-wp-rest-request.php
@@ -265,9 +265,7 @@ public function add_header( $key, $value ) {
 		$key   = $this->canonicalize_header_name( $key );
 		$value = (array) $value;
 
-		if ( ! isset( $this->headers[ $key ] ) ) {
-			$this->headers[ $key ] = array();
-		}
+		$this->headers[ $key ] ??= array();
 
 		$this->headers[ $key ] = array_merge( $this->headers[ $key ], $value );
 	}
diff --git a/src/wp-includes/rest-api/class-wp-rest-server.php b/src/wp-includes/rest-api/class-wp-rest-server.php
index c331d73363541..a8002800e5d3e 100644
--- a/src/wp-includes/rest-api/class-wp-rest-server.php
+++ b/src/wp-includes/rest-api/class-wp-rest-server.php
@@ -989,9 +989,7 @@ public function get_routes( $route_namespace = '' ) {
 				$handlers = array( $handlers );
 			}
 
-			if ( ! isset( $this->route_options[ $route ] ) ) {
-				$this->route_options[ $route ] = array();
-			}
+			$this->route_options[ $route ] ??= array();
 
 			foreach ( $handlers as $key => &$handler ) {
 
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php
index f336f321a9ea2..6ef6d09b0333b 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php
@@ -2139,9 +2139,7 @@ protected function get_media_types() {
 		foreach ( get_allowed_mime_types() as $mime_type ) {
 			$parts = explode( '/', $mime_type );
 
-			if ( ! isset( $media_types[ $parts[0] ] ) ) {
-				$media_types[ $parts[0] ] = array();
-			}
+			$media_types[ $parts[0] ] ??= array();
 
 			$media_types[ $parts[0] ][] = $mime_type;
 		}
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-menus-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-menus-controller.php
index 706e36fb6cc66..887662e06ad33 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-menus-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-menus-controller.php
@@ -436,9 +436,7 @@ protected function handle_auto_add( $menu_id, $request ) {
 
 		$nav_menu_option = (array) get_option( 'nav_menu_options', array( 'auto_add' => array() ) );
 
-		if ( ! isset( $nav_menu_option['auto_add'] ) ) {
-			$nav_menu_option['auto_add'] = array();
-		}
+		$nav_menu_option['auto_add'] ??= array();
 
 		$auto_add = $request['auto_add'];
 
diff --git a/src/wp-includes/taxonomy.php b/src/wp-includes/taxonomy.php
index 29317f0a8bf9b..e7d63c1210117 100644
--- a/src/wp-includes/taxonomy.php
+++ b/src/wp-includes/taxonomy.php
@@ -3603,10 +3603,8 @@ function wp_update_term_count( $terms, $taxonomy, $do_deferred = false ) {
 	}
 
 	if ( wp_defer_term_counting() ) {
-		if ( ! isset( $_deferred[ $taxonomy ] ) ) {
-			$_deferred[ $taxonomy ] = array();
-		}
-		$_deferred[ $taxonomy ] = array_unique( array_merge( $_deferred[ $taxonomy ], $terms ) );
+		$_deferred[ $taxonomy ] ??= array();
+		$_deferred[ $taxonomy ]   = array_unique( array_merge( $_deferred[ $taxonomy ], $terms ) );
 		return true;
 	}
 
@@ -3909,9 +3907,7 @@ function update_object_term_cache( $object_ids, $object_type ) {
 	foreach ( $non_cached_ids as $id ) {
 		foreach ( $taxonomies as $taxonomy ) {
 			if ( ! isset( $object_terms[ $id ][ $taxonomy ] ) ) {
-				if ( ! isset( $object_terms[ $id ] ) ) {
-					$object_terms[ $id ] = array();
-				}
+				$object_terms[ $id ]            ??= array();
 				$object_terms[ $id ][ $taxonomy ] = array();
 			}
 		}
@@ -4401,10 +4397,8 @@ function _split_shared_term( $term_id, $term_taxonomy_id, $record = true ) {
 
 	// Keep a record of term_ids that have been split, keyed by old term_id. See wp_get_split_term().
 	if ( $record ) {
-		$split_term_data = get_option( '_split_terms', array() );
-		if ( ! isset( $split_term_data[ $term_id ] ) ) {
-			$split_term_data[ $term_id ] = array();
-		}
+		$split_term_data               = get_option( '_split_terms', array() );
+		$split_term_data[ $term_id ] ??= array();
 
 		$split_term_data[ $term_id ][ $term_taxonomy->taxonomy ] = $new_term_id;
 		update_option( '_split_terms', $split_term_data );
@@ -4509,9 +4503,7 @@ function _wp_batch_split_terms() {
 			continue;
 		}
 
-		if ( ! isset( $split_term_data[ $term_id ] ) ) {
-			$split_term_data[ $term_id ] = array();
-		}
+		$split_term_data[ $term_id ] ??= array();
 
 		// Keep track of taxonomies whose hierarchies need flushing.
 		if ( ! isset( $taxonomies[ $shared_tt->taxonomy ] ) ) {