wp_get_original_referer() │ WP 2.0.4

Retrieves original referer that was posted, if it exists.

No Hooks.

Returns

String|false. Original referer URL on success, false on failure.

Usage

wp_get_original_referer();

Changelog

Since 2.0.4 Introduced.

wp_get_original_referer() code WP 7.0

wp-includes/functions.php 
function wp_get_original_referer() {
	// Return early if called before wp_validate_redirect() is defined.
	if ( ! function_exists( 'wp_validate_redirect' ) ) {
		return false;
	}

	if ( ! empty( $_REQUEST['_wp_original_http_referer'] ) ) {
		return wp_validate_redirect( wp_unslash( $_REQUEST['_wp_original_http_referer'] ), false );
	}

	return false;
}