$d = "sdaf";
var_dump(filter_var($d, FILTER_VALIDATE_INT));

$d = "9876543210";
var_dump(filter_var($d, FILTER_VALIDATE_INT));

var_dump(filter_var(9876543210, FILTER_VALIDATE_INT));

var_dump(filter_var(9876543210, FILTER_VALIDATE_INT));