$ch=curl_init("www.googleapis.com/admin/directory/v1/users");
curl_setopt($ch,CURLOPT_HEADER,0);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
$result=curl_exec($ch);
curl_close($ch);
with curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
it will return the result on success, FALSE on failure.
with curl_setopt($ch,CURLOPT_RETURNTRANSFER,false);
it will return TRUE on success or FALSE on failure.