* @param string          $param   The parameter name.
	 * @return string|WP_Error The sanitized username, if valid, otherwise an error.
	 */
	public function check_username( $value, $request, $param ) {
		$username = (string) $value;

		if ( ! validate_username( $username ) ) {
			return new WP_Error(
				'rest_user_invalid_username',
				__( 'This username is invalid because it uses illegal characters. Please enter a valid username.' ),
				array( 'status' => 400 )
			);
		}

		/** This filter is documented in wp-includes/user.php */
		$illegal_logins = (array) apply_filters( 'illegal_user_logins', array() );

		if ( in_array( strtolower( $username ), array_map( 'strtolower', $illegal_logins ), true ) ) {
			return new WP_Error(
				'rest_user_invalid_username',
				__( 'Sorry, that username is not allowed.' ),
				array( 'status' => 400 )
			);
		}

		return $username;
	}

	/**
	 * Check a user password for the REST API.
	 *
	 * Performs a couple of checks like edit_user() in wp-admin/includes/user.php.
	 *
	 * @since 4.7.0
	 *
	 * @param string          $value   The password submitted in the request.
	 * @param WP_REST_Request $request Full details about the request.
	 * @param string          $param   The parameter name.
	 * @return string|WP_Error The sanitized password, if valid, otherwise an error.
	 */
	public function check_user_password( $value, $request, $param ) {
		$password = (string) $value;

		if ( empty( $password ) ) {
			return new WP_Error(
				'rest_user_invalid_password',
				__( 'Passwords cannot be empty.' ),
				array( 'status' => 400 )
			);
		}

		if ( str_contains( $password, '\\' ) ) {
			return new WP_Error(
				'rest_user_invalid_password',
				sprintf(
					/* translators: %s: The '\' character. */
					__( 'Passwords cannot contain the "%s" character.' ),
					'\\'
				),
				array( 'status' => 400 )
			);
		}

		return $password;
	}

	/**
	 * Retrieves the user's schema, conforming to JSON Schema.
	 *
	 * @since 4.7.0
	 *
	 * @return array Item schema data.
	 */
	public function get_item_schema() {
		if ( $this->schema ) {
			return $this->add_additional_fields_schema( $this->schema );
		}

		$schema = array(
			'$schema'    => 'http://json-schema.org/draft-04/schema#',
			'title'      => 'user',
			'type'       => 'object',
			'properties' => array(
				'id'                 => array(
					'description' => __( 'Unique identifier for the user.' ),
					'type'        => 'integer',
					'context'     => array( 'embed', 'view', 'edit' ),
					'readonly'    => true,
				),
				'username'           => array(
					'description' => __( 'Login name for the user.' ),
					'type'        => 'string',
					'context'     => array( 'edit' ),
					'required'    => true,
					'arg_options' => array(
						'sanitize_callback' => array( $this, 'check_username' ),
					),
				),
				'name'               => array(
					'description' => __( 'Display name for the user.' ),
					'type'        => 'string',
					'context'     => array( 'embed', 'view', 'edit' ),
					'arg_options' => array(
						'sanitize_callback' => 'sanitize_text_field',
					),
				),
				'first_name'         => array(
					'description' => __( 'First name for the user.' ),
					'type'        => 'string',
					'context'     => array( 'edit' ),
					'arg_options' => array(
						'sanitize_callback' => 'sanitize_text_field',
					),
				),
				'last_name'          => array(
					'description' => __( 'Last name for the user.' ),
					'type'        => 'string',
					'context'     => array( 'edit' ),
					'arg_options' => array(
						'sanitize_callback' => 'sanitize_text_field',
					),
				),
				'email'              => array(
					'description' => __( 'The email address for the user.' ),
					'type'        => 'string',
					'format'      => 'email',
					'context'     => array( 'edit' ),
					'required'    => true,
				),
				'url'                => array(
					'description' => __( 'URL of the user.' ),
					'type'        => 'string',
					'format'      => 'uri',
					'context'     => array( 'embed', 'view', 'edit' ),
				),
				'description'        => array(
					'description' => __( 'Description of the user.' ),
					'type'        => 'string',
					'context'     => array( 'embed', 'view', 'edit' ),
				),
				'link'               => array(
					'description' => __( 'Author URL of the user.' ),
					'type'        => 'string',
					'format'      => 'uri',
					'context'     => array( 'embed', 'view', 'edit' ),
					'readonly'    => true,
				),
				'locale'             => array(
					'description' => __( 'Locale for the user.' ),
					'type'        => 'string',
					'enum'        => array_merge( array( '', 'en_US' ), get_available_languages() ),
					'context'     => array( 'edit' ),
				),
				'nickname'           => array(
					'description' => __( 'The nickname for the user.' ),
					'type'        => 'string',
					'context'     => array( 'edit' ),
					'arg_options' => array(
						'sanitize_callback' => 'sanitize_text_field',
					),
				),
				'slug'               => array(
					'description' => __( 'An alphanumeric identifier for the user.' ),
					'type'        => 'string',
					'context'     => array( 'embed', 'view', 'edit' ),
					'arg_options' => array(
						'sanitize_callback' => array( $this, 'sanitize_slug' ),
					),
				),
				'registered_date'    => array(
					'description' => __( 'Registration date for the user.' ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'edit' ),
					'readonly'    => true,
				),
				'roles'              => array(
					'description' => __( 'Roles assigned to the user.' ),
					'type'        => 'array',
					'items'       => array(
						'type' => 'string',
					),
					'context'     => array( 'edit' ),
				),
				'password'           => array(
					'description' => __( 'Password for the user (never included).' ),
					'type'        => 'string',
					'context'     => array(), // Password is never displayed.
					'required'    => true,
					'arg_options' => array(
						'sanitize_callback' => array( $this, 'check_user_password' ),
					),
				),
				'capabilities'       => array(
					'description' => __( 'All capabilities assigned to the user.' ),
					'type'        => 'object',
					'context'     => array( 'edit' ),
					'readonly'    => true,
				),
				'extra_capabilities' => array(
					'description' => __( 'Any extra capabilities assigned to the user.' ),
					'type'        => 'object',
					'context'     => array( 'edit' ),
					'readonly'    => true,
				),
			),
		);

		if ( get_option( 'show_avatars' ) ) {
			$avatar_properties = array();

			$avatar_sizes = rest_get_avatar_sizes();

			foreach ( $avatar_sizes as $size ) {
				$avatar_properties[ $size ] = array(
					/* translators: %d: Avatar image size in pixels. */
					'description' => sprintf( __( 'Avatar URL with image size of %d pixels.' ), $size ),
					'type'        => 'string',
					'format'      => 'uri',
					'context'     => array( 'embed', 'view', 'edit' ),
				);
			}

			$schema['properties']['avatar_urls'] = array(
				'description' => __( 'Avatar URLs for the user.' ),
				'type'        => 'object',
				'context'     => array( 'embed', 'view', 'edit' ),
				'readonly'    => true,
				'properties'  => $avatar_properties,
			);
		}

		$schema['properties']['meta'] = $this->meta->get_field_schema();

		$this->schema = $schema;

		return $this->add_additional_fields_schema( $this->schema );
	}

	/**
	 * Retrieves the query params for collections.
	 *
	 * @since 4.7.0
	 *
	 * @return array Collection parameters.
	 */
	public function get_collection_params() {
		$query_params = parent::get_collection_params();

		$query_params['context']['default'] = 'view';

		$query_params['exclude'] = array(
			'description' => __( 'Ensure result set excludes specific IDs.' ),
			'type'        => 'array',
			'items'       => array(
				'type' => 'integer',
			),
			'default'     => array(),
		);

		$query_params['include'] = array(
			'description' => __( 'Limit result set to specific IDs.' ),
			'type'        => 'array',
			'items'       => array(
				'type' => 'integer',
			),
			'default'     => array(),
		);

		$query_params['offset'] = array(
			'description' => __( 'Offset the result set by a specific number of items.' ),
			'type'        => 'integer',
		);

		$query_params['order'] = array(
			'default'     => 'asc',
			'description' => __( 'Order sort attribute ascending or descending.' ),
			'enum'        => array( 'asc', 'desc' ),
			'type'        => 'string',
		);

		$query_params['orderby'] = array(
			'default'     => 'name',
			'description' => __( 'Sort collection by user attribute.' ),
			'enum'        => array(
				'id',
				'include',
				'name',
				'registered_date',
				'slug',
				'include_slugs',
				'email',
				'url',
			),
			'type'        => 'string',
		);

		$query_params['slug'] = array(
			'description' => __( 'Limit result set to users with one or more specific slugs.' ),
			'type'        => 'array',
			'items'       => array(
				'type' => 'string',
			),
		);

		$query_params['roles'] = array(
			'description' => __( 'Limit result set to users matching at least one specific role provided. Accepts csv list or single role.' ),
			'type'        => 'array',
			'items'       => array(
				'type' => 'string',
			),
		);

		$query_params['capabilities'] = array(
			'description' => __( 'Limit result set to users matching at least one specific capability provided. Accepts csv list or single capability.' ),
			'type'        => 'array',
			'items'       => array(
				'type' => 'string',
			),
		);

		$query_params['who'] = array(
			'description' => __( 'Limit result set to users who are considered authors.' ),
			'type'        => 'string',
			'enum'        => array(
				'authors',
			),
		);

		$query_params['has_published_posts'] = array(
			'description' => __( 'Limit result set to users who have published posts.' ),
			'type'        => array( 'boolean', 'array' ),
			'items'       => array(
				'type' => 'string',
				'enum' => get_post_types( array( 'show_in_rest' => true ), 'names' ),
			),
		);

		/**
		 * Filters REST API collection parameters for the users controller.
		 *
		 * This filter registers the collection parameter, but does not map the
		 * collection parameter to an internal WP_User_Query parameter.  Use the
		 * `rest_user_query` filter to set WP_User_Query arguments.
		 *
		 * @since 4.7.0
		 *
		 * @param array $query_params JSON Schema-formatted collection parameters.
		 */
		return apply_filters( 'rest_user_collection_params', $query_params );
	}
}
<br />
<b>Fatal error</b>:  require(): Failed opening required '/home/healths/public_html/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php' (include_path='.:') in <b>/home/healths/public_html/wp-settings.php</b> on line <b>285</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function set() on null in /home/healths/public_html/wp-includes/l10n.php:806
Stack trace:
#0 /home/healths/public_html/wp-includes/l10n.php(900): load_textdomain()
#1 /home/healths/public_html/wp-includes/class-wp-fatal-error-handler.php(47): load_default_textdomain()
#2 [internal function]: WP_Fatal_Error_Handler-&gt;handle()
#3 {main}
  thrown in <b>/home/healths/public_html/wp-includes/l10n.php</b> on line <b>806</b><br />