diff --git a/wp-includes/rest-api.php b/wp-includes/rest-api.php
index 9a615419b9..7480fd5c64 100644
--- a/wp-includes/rest-api.php
+++ b/wp-includes/rest-api.php
@@ -118,8 +118,8 @@ function register_rest_route( $namespace, $route, $args = array(), $override = f
  * @global array $wp_rest_additional_fields Holds registered fields, organized
  *                                          by object type.
  *
- * @param string|array $object_type Object(s) the field is being registered
- *                                  to, "post"|"term"|"comment" etc.
+ * @param string|array $object_type Object(s) the field is being registered to,
+ *                                  "post"|"term"|"comment" etc.
  * @param string       $attribute   The attribute name.
  * @param array        $args {
  *     Optional. An array of arguments used to handle the registered field.
@@ -135,6 +135,8 @@ function register_rest_route( $namespace, $route, $args = array(), $override = f
  * }
  */
 function register_rest_field( $object_type, $attribute, $args = array() ) {
+	global $wp_rest_additional_fields;
+
 	$defaults = array(
 		'get_callback'    => null,
 		'update_callback' => null,
@@ -143,8 +145,6 @@ function register_rest_field( $object_type, $attribute, $args = array() ) {
 
 	$args = wp_parse_args( $args, $defaults );
 
-	global $wp_rest_additional_fields;
-
 	$object_types = (array) $object_type;
 
 	foreach ( $object_types as $object_type ) {
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-block-renderer-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-block-renderer-controller.php
index 69a45dce88..3e4e8eb794 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-block-renderer-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-block-renderer-controller.php
@@ -103,6 +103,8 @@ class WP_REST_Block_Renderer_Controller extends WP_REST_Controller {
 	 *
 	 * @since 5.0.0
 	 *
+	 * @global WP_Post $post Global post object.
+	 *
 	 * @param WP_REST_Request $request Request.
 	 * @return true|WP_Error True if the request has read access, WP_Error object otherwise.
 	 */
@@ -111,7 +113,7 @@ class WP_REST_Block_Renderer_Controller extends WP_REST_Controller {
 
 		$post_id = isset( $request['post_id'] ) ? (int) $request['post_id'] : 0;
 
-		if ( 0 < $post_id ) {
+		if ( $post_id > 0 ) {
 			$post = get_post( $post_id );
 
 			if ( ! $post || ! current_user_can( 'edit_post', $post->ID ) ) {
@@ -143,6 +145,8 @@ class WP_REST_Block_Renderer_Controller extends WP_REST_Controller {
 	 *
 	 * @since 5.0.0
 	 *
+	 * @global WP_Post $post Global post object.
+	 *
 	 * @param WP_REST_Request $request Full details about the request.
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
@@ -151,7 +155,7 @@ class WP_REST_Block_Renderer_Controller extends WP_REST_Controller {
 
 		$post_id = isset( $request['post_id'] ) ? (int) $request['post_id'] : 0;
 
-		if ( 0 < $post_id ) {
+		if ( $post_id > 0 ) {
 			$post = get_post( $post_id );
 
 			// Set up postdata since this will be needed if post_id was set.
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-controller.php
index 3417a6fe75..b1cb4be457 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-controller.php
@@ -504,11 +504,14 @@ abstract class WP_REST_Controller {
 	 *
 	 * @since 4.7.0
 	 *
+	 * @global array $wp_rest_additional_fields Holds registered fields, organized by object type.
+	 *
 	 * @param string $object_type Optional. The object type.
-	 * @return array Registered additional fields (if any), empty array if none or if the object type could
-	 *               not be inferred.
+	 * @return array Registered additional fields (if any), empty array if none or if the object type
+	 *               could not be inferred.
 	 */
 	protected function get_additional_fields( $object_type = null ) {
+		global $wp_rest_additional_fields;
 
 		if ( ! $object_type ) {
 			$object_type = $this->get_object_type();
@@ -518,8 +521,6 @@ abstract class WP_REST_Controller {
 			return array();
 		}
 
-		global $wp_rest_additional_fields;
-
 		if ( ! $wp_rest_additional_fields || ! isset( $wp_rest_additional_fields[ $object_type ] ) ) {
 			return array();
 		}
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php
index 7cb895670a..a4a843bf83 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php
@@ -265,10 +265,14 @@ class WP_REST_Plugins_Controller extends WP_REST_Controller {
 	 *
 	 * @since 5.5.0
 	 *
+	 * @global WP_Filesystem_Base $wp_filesystem WordPress filesystem subclass.
+	 *
 	 * @param WP_REST_Request $request Full details about the request.
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function create_item( $request ) {
+		global $wp_filesystem;
+
 		require_once ABSPATH . 'wp-admin/includes/file.php';
 		require_once ABSPATH . 'wp-admin/includes/plugin.php';
 		require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
@@ -329,19 +333,32 @@ class WP_REST_Plugins_Controller extends WP_REST_Controller {
 		}
 
 		if ( is_null( $result ) ) {
-			global $wp_filesystem;
 			// Pass through the error from WP_Filesystem if one was raised.
-			if ( $wp_filesystem instanceof WP_Filesystem_Base && is_wp_error( $wp_filesystem->errors ) && $wp_filesystem->errors->has_errors() ) {
-				return new WP_Error( 'unable_to_connect_to_filesystem', $wp_filesystem->errors->get_error_message(), array( 'status' => 500 ) );
+			if ( $wp_filesystem instanceof WP_Filesystem_Base
+				&& is_wp_error( $wp_filesystem->errors ) && $wp_filesystem->errors->has_errors()
+			) {
+				return new WP_Error(
+					'unable_to_connect_to_filesystem',
+					$wp_filesystem->errors->get_error_message(),
+					array( 'status' => 500 )
+				);
 			}
 
-			return new WP_Error( 'unable_to_connect_to_filesystem', __( 'Unable to connect to the filesystem. Please confirm your credentials.' ), array( 'status' => 500 ) );
+			return new WP_Error(
+				'unable_to_connect_to_filesystem',
+				__( 'Unable to connect to the filesystem. Please confirm your credentials.' ),
+				array( 'status' => 500 )
+			);
 		}
 
 		$file = $upgrader->plugin_info();
 
 		if ( ! $file ) {
-			return new WP_Error( 'unable_to_determine_installed_plugin', __( 'Unable to determine what plugin was installed.' ), array( 'status' => 500 ) );
+			return new WP_Error(
+				'unable_to_determine_installed_plugin',
+				__( 'Unable to determine what plugin was installed.' ),
+				array( 'status' => 500 )
+			);
 		}
 
 		if ( 'inactive' !== $request['status'] ) {
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
index 962ff4b3d9..63ad45b8ec 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
@@ -1173,6 +1173,8 @@ class WP_REST_Users_Controller extends WP_REST_Controller {
 	 *
 	 * @since 4.7.0
 	 *
+	 * @global WP_Roles $wp_roles WordPress role management object.
+	 *
 	 * @param int   $user_id User ID.
 	 * @param array $roles   New user roles.
 	 * @return true|WP_Error True if the current user is allowed to make the role change,
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 2c9f79a0bf..4fde953975 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51277';
+$wp_version = '5.9-alpha-51278';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.