Question

I have a form and upon submitting it, I would like to ensure the following:

1. the beginning of whatever is typed in the input field starts with mod_
2. After mod_, only alpha numeric characters can be used.

For the first stage, I got this far:

if (preg_match('/^mod_/', $str)) {
        //script goes here
}

However for the second stage, I’m not entirely sure if is the best method/works:

if (preg_match('/^mod_/[A-Za-z0-9]$/', $str)) {
        //script goes here
}

I have probably made a mistake in the second stage of the preg_match(), however, if I haven’t, could someone please let me know if what I have used is ok, else what could be done to improve it.

Answer 1

This should do it:

if (preg_match('/^mod_[A-Za-z0-9]+$/', $str)) {

The + that I added before the $ means “match the previous thing 1 or more times.” In this case, that is 1 or more ASCII characters or digits.