Extract a single (unsigned) integer from a string

If you just want to filter everything other than the numbers out, the easiest is to use filter_var:

$str = 'In My Cart : 11 items';
$int = (int) filter_var($str, FILTER_SANITIZE_NUMBER_INT);

$str = 'In My Cart : 11 12 items';
preg_match_all('!\d+!', $str, $matches);
print_r($matches);