Request token

<?php
    
    /** 
    * Send a POST requst using cURL 
    * @param string $CLIENT_ID the client ID
    * @param string $CLIENT_SECRET the client secret
    * @return string 
    */  
    function get_token($CLIENT_ID, $CLIENT_SECRET, $AUTH_URL) {

        // Request token
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $AUTH_URL);
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, "grant_type=jwt_bearer&client_id=$CLIENT_ID&client_secret=$CLIENT_SECRET");
        $result = curl_exec($ch);
        curl_close($ch); 
            
        // Prepare response
        header('Content-type: application/json');
        
        // return JWT to requesting app
        if($result == FALSE) {
            // Something went wrong.
            echo json_encode(array("error" => "CURL request failed."));
            return false;
        }
        else {
            $result_decoded = json_decode($result);
            
            if(array_key_exists("error", $result_decoded) or !array_key_exists("access_token", $result_decoded)) {
                // Use this for additional error handling.
                return $result;
            }
            else {
                // Print successful response.
                return $result;
            }
        }
    }

?>