curl_exec not hit server

Hi, I use the following code to call third party web service: curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_TIMEOUT, 120); curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1); curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 1); curl_setopt($ch, CURLOPT_SSLVERSION, 3); curl_setopt($ch, CURLOPT_SSLCERT, $loc); curl_setopt($ch, CURLOPT_SSLCERTPASSWD, $password); curl_setopt($ch, CURLOPT_HTTPHEADER, $this->_httpHeaders); curl_setopt($ch, CURLOPT_POST, 1); curl_setopt($ch, CURLOPT_POSTFIELDS, $this->_xmlData); $ret = curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); $xmlResponseData = curl_exec($ch); But for a specific API, curl_exec() returns true but there was no hit on their server (as verified by contact in that company from server log) Can someone provide hint ? Thanks