regex not working for php form validation

Question

Usernames on my website should only contain A-Z,a-z,0-9. No spaces or special characters.

I have the following php code in my register form however when I input a username which contains only letters it outputs the error, any help?:

if (!preg_match('/[^a-zA-Z0-9]+/gm', $_POST["userName"])) {
    $output = json_encode(
       array(
         'type' => 'error',
         'text' => 'Your username must not contain any spaces or special characters.'
          ));
    die($output);
}

<3 Regex101 https://regex101.com/r/W67Jf9/1, `^` should be outside the list — SubjectCurio, Nov 27 '18 at 20:09

score 0 · Answer 1 · answered Nov 27 '18 at 20:13

0

your syntax is wrong,Try these

<?php   
 if (!preg_match('/^[a-zA-Z0-9]+$/', "name")) {
         echo "incorrect";
    }else{
      echo "correct";
    }
?>

answered Nov 27 '18 at 20:13

Balaji Rajendran

357
5
17

What is this fixing? `"name"` will always match and this does the opposite of what OP is doing – user3783243 Nov 27 '18 at 20:15
!preg_match('/^[a-zA-Z0-9]+$/', "name") syntax error – Balaji Rajendran Nov 27 '18 at 20:16
@user3783243 fixes my syntax, I had ^ inside the list, and $ is the end of the string. – Ashley Nunn Nov 27 '18 at 20:16
@AshleyNunn That's a typo, not invalid syntax. It was creating a negative character class, just remove `!` from the `preg_match` and the `g` modifier and would have worked. – user3783243 Nov 27 '18 at 20:24

regex not working for php form validation

1 Answers1