OK, did that:
<?php
$token = "fdf.....e4";
$VEHICLE_ID = "7....6";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://owner-api.teslamotors.com/api/1/vehicles/".$VEHICLE_ID."/command/honk_horn");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($ch, CURLOPT_HEADER, FALSE)...