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function is not described

is_allowed_http_origin() WP 3.4.0

Determines if the HTTP origin is an authorized one.

Hooks in function
Return

String. Origin URL if allowed, empty string if not.

Usage

is_allowed_http_origin( $origin );
$origin(null/string)
Origin URL. If not provided, the value of get_http_origin() is used.
Default: null

Code of is allowed http origin: wp-includes/http.php VER 5.1.1

<?php
function is_allowed_http_origin( $origin = null ) {
	$origin_arg = $origin;

	if ( null === $origin ) {
		$origin = get_http_origin();
	}

	if ( $origin && ! in_array( $origin, get_allowed_http_origins() ) ) {
		$origin = '';
	}

	/**
	 * Change the allowed HTTP origin result.
	 *
	 * @since 3.4.0
	 *
	 * @param string $origin     Origin URL if allowed, empty string if not.
	 * @param string $origin_arg Original origin string passed into is_allowed_http_origin function.
	 */
	return apply_filters( 'allowed_http_origin', $origin, $origin_arg );
}