WP_REST_Server::match_request_to_handler() WordPress Method

	protected function match_request_to_handler( $request ) {
		$method = $request->get_method();
		$path   = $request->get_route();

		$with_namespace = array();

		foreach ( $this->get_namespaces() as $namespace ) {
			if ( 0 === strpos( trailingslashit( ltrim( $path, '/' ) ), $namespace ) ) {
				$with_namespace[] = $this->get_routes( $namespace );
			}
		}

		if ( $with_namespace ) {
			$routes = array_merge( ...$with_namespace );
		} else {
			$routes = $this->get_routes();
		}

		foreach ( $routes as $route => $handlers ) {
			$match = preg_match( '@^' . $route . '$@i', $path, $matches );

			if ( ! $match ) {
				continue;
			}

			$args = array();

			foreach ( $matches as $param => $value ) {
				if ( ! is_int( $param ) ) {
					$args[ $param ] = $value;
				}
			}

			foreach ( $handlers as $handler ) {
				$callback = $handler['callback'];
				$response = null;

				// Fallback to GET method if no HEAD method is registered.
				$checked_method = $method;
				if ( 'HEAD' === $method && empty( $handler['methods']['HEAD'] ) ) {
					$checked_method = 'GET';
				}
				if ( empty( $handler['methods'][ $checked_method ] ) ) {
					continue;
				}

				if ( ! is_callable( $callback ) ) {
					return array( $route, $handler );
				}

				$request->set_url_params( $args );
				$request->set_attributes( $handler );

				$defaults = array();

				foreach ( $handler['args'] as $arg => $options ) {
					if ( isset( $options['default'] ) ) {
						$defaults[ $arg ] = $options['default'];
					}
				}

				$request->set_default_params( $defaults );

				return array( $route, $handler );
			}
		}

		return new WP_Error(
			'rest_no_route',
			__( 'No route was found matching the URL and request method.' ),
			array( 'status' => 404 )
		);
	}