You can check if curl is present in a web server, just use the below snipped to check if curl available. Below code will check if curl is available on the server.
<?php function iscurlinstalled() { if (in_array ('curl', get_loaded_extensions())) { return true; } else{ return false; } } ?>
Usage:
<?php echo (iscurlinstalled())?'curl found':'no curl found'; ?>