register_rest_route( string $route_namespace, string $route, array $args = array(), bool $override = false ): bool

34function register_rest_route( $route_namespace, $route, $args = array(), $override = false ) {35	if ( empty( $route_namespace ) ) {36		/*37		 * Non-namespaced routes are not allowed, with the exception of the main38		 * and namespace indexes. If you really need to register a39		 * non-namespaced route, call `WP_REST_Server::register_route` directly.40		 */41		_doing_it_wrong(42			__FUNCTION__,43			sprintf(44				/* translators: 1: string value of the namespace, 2: string value of the route. */45				__( 'Routes must be namespaced with plugin or theme name and version. Instead there seems to be an empty namespace \'%1$s\' for route \'%2$s\'.' ),46				'<code>' . $route_namespace . '</code>',47				'<code>' . $route . '</code>'48			),49			'4.4.0'50		);51		return false;52	} elseif ( empty( $route ) ) {53		_doing_it_wrong(54			__FUNCTION__,55			sprintf(56				/* translators: 1: string value of the namespace, 2: string value of the route. */57				__( 'Route must be specified. Instead within the namespace \'%1$s\', there seems to be an empty route \'%2$s\'.' ),58				'<code>' . $route_namespace . '</code>',59				'<code>' . $route . '</code>'60			),61			'4.4.0'62		);63		return false;64	}65 66	$clean_namespace = trim( $route_namespace, '/' );67 68	if ( $clean_namespace !== $route_namespace ) {69		_doing_it_wrong(70			__FUNCTION__,71			sprintf(72				/* translators: 1: string value of the namespace, 2: string value of the route. */73				__( 'Namespace must not start or end with a slash. Instead namespace \'%1$s\' for route \'%2$s\' seems to contain a slash.' ),74				'<code>' . $route_namespace . '</code>',75				'<code>' . $route . '</code>'76			),77			'5.4.2'78		);79	}80 81	if ( ! did_action( 'rest_api_init' ) ) {82		_doing_it_wrong(83			__FUNCTION__,84			sprintf(85				/* translators: 1: rest_api_init, 2: string value of the route, 3: string value of the namespace. */86				__( 'REST API routes must be registered on the %1$s action. Instead route \'%2$s\' with namespace \'%3$s\' was not registered on this action.' ),87				'<code>rest_api_init</code>',88				'<code>' . $route . '</code>',89				'<code>' . $route_namespace . '</code>'90			),91			'5.1.0'92		);93	}94 95	if ( isset( $args['args'] ) ) {96		$common_args = $args['args'];97		unset( $args['args'] );98	} else {99		$common_args = array();100	}101 102	if ( isset( $args['callback'] ) ) {103		// Upgrade a single set to multiple.104		$args = array( $args );105	}106 107	$defaults = array(108		'methods'  => 'GET',109		'callback' => null,110		'args'     => array(),111	);112 113	foreach ( $args as $key => &$arg_group ) {