Question

I’m trying to use regex to validate input from the user, I’m wanting to allow any letter in the alphabet, numbers, spaces and the following symbols:

! £ $ % & * ( ) _ + [ ] : ; @ ~ # < > ? , . –

I’ve never been that good with regex as it confuses the hell out of me. This is the best I’ve got but it’s not working properly because if I put a ? in the field I receive the error.

<?php
    $title = $_POST['title'];

    if (!preg_match('/\/^[a-zA-Z0-9\s!£$%&*()_+[\]:;@~#<>?,.-]+$\//m', $title)) {
        $error = "Photo name contains unsafe characters.";
        $solution = "<a href=\"javascript:history.go(-1)\">Try again?</a>";
    }

    if ($error) { echo("$error");
?>

Why am I always getting these regex things wrong, just when I think I’m beginning to understand, I soon realise I’m really not! 😛

If anyone could help me out and maybe explain why my example doesn’t work so I can learn from my mistakes that would be very appreciated, thank you!

Answer 1

You have some extra / before the ^ and after the $, this one should work:

preg_match('/^[a-zA-Z0-9\s!£$%&*()_+[\]:;@~#<>?,.-]+$/m', $title)

Also the m modifier would cause $ to match the end of the line, and allow someone to add any character after the first line, so you should remove it.