Source

File: wp-includes/rest-api/class-wp-rest-request.php

public function __construct( $method = '', $route = '', $attributes = array() ) {
		$this->params = array(
			'URL'      => array(),
			'GET'      => array(),
			'POST'     => array(),
			'FILES'    => array(),

			// See parse_json_params.
			'JSON'     => null,

			'defaults' => array(),
		);

		$this->set_method( $method );
		$this->set_route( $route );
		$this->set_attributes( $attributes );
	}