用PHP将用户名与正则表达式进行比较

Question

I've never used regular expressions before and did some research on how to allow my username field only alphanumeric characters, dashes, dots, and underscores. I have the following expression but it doesn't seem to be working.

$string = "Joe_Scotto";

if (!preg_match('[a-zA-Z0-9_-.]', $string)) {
    echo "Does not match Regex";
} else {
    echo "Matches";
}

I want the statement to return true if it is following the "guidelines" and false if the username contains something other than what I specified it should contain. Any help would be great. Thanks!

Answer 1

Try this

$string = "Joe_Scotto";

if (!preg_match('/^[A-Za-z0-9_.]+$/', $string)) {
    echo "Does not match Regex";
} else {
    echo "Matches";
}