WordPress at a glance
function is not described

WP_REST_Request::has_param() public WP 5.3.0

Checks if a parameter exists in the request.

This allows distinguishing between an omitted parameter, and a parameter specifically set to null.

{} It's a method of the class: WP_REST_Request{}

No Hooks.

Return

true/false. True if a param exists for the given key.

Usage

$WP_REST_Request = new WP_REST_Request();
$WP_REST_Request->has_param( $key );
$key(string) (required)
Parameter name.

Changelog

Since 5.3.0 Introduced.

Code of WP_REST_Request::has_param() WP 5.5.1

<?php
public function has_param( $key ) {
	$order = $this->get_parameter_order();

	foreach ( $order as $type ) {
		if ( is_array( $this->params[ $type ] ) && array_key_exists( $key, $this->params[ $type ] ) ) {
			return true;
		}
	}

	return false;
}