WordPress at a glance
function is not described

WP_REST_Server::send_header() public WP 4.4.0

Sends an HTTP header.

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

No Hooks.

Return

Null. Nothing.

Usage

$WP_REST_Server = new WP_REST_Server();
$WP_REST_Server->send_header( $key, $value );
$key(string) (required)
Header key.
$value(string) (required)
Header value.

Changelog

Since 4.4.0 Introduced.

Code of WP_REST_Server::send_header() WP 5.5.2

<?php
public function send_header( $key, $value ) {
	/*
	 * Sanitize as per RFC2616 (Section 4.2):
	 *
	 * Any LWS that occurs between field-content MAY be replaced with a
	 * single SP before interpreting the field value or forwarding the
	 * message downstream.
	 */
	$value = preg_replace( '/\s+/', ' ', $value );
	header( sprintf( '%s: %s', $key, $value ) );
}