Regular expression "." Please answer. Thank you.

Question

<?

$zz = '/gg.gg/';

$string = "ABC1ABC";

$if(preg_match($zz, $string,$matches)){

echo 'Matched, the result is:';

var_dump($matches);

}else{

echo 'No match';

}

?>

Why the match failed, I don't understand. . .

Answer 1

$string = "ggABC1ABCgg"；

Answer 2

What the hell is '/gg.+gg/'?