PHP Verify if a string dosnt contain anything else except alpha-numeric or characters gived

So, im coding something and for the username, and i want to verify if there isnt any other characters then ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890._ // a space too but, there is too much characters to add in a preg_match, and i would like just to verify if there is any other characters then the list i put, but how..?

I tried preg_match, but got tired after i saw all characters when doing Windos + . …there is too much characters…and i just want to simplify my code..so how?

>Solution :

RegEx will do the trick.

Edit: I see now that you’d like to allow only specified characters, iterating the string will be sufficient for this.

<?php

function validateUsername($username, $minLength = 3, $maxLength = 20) {

    $allowed_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890._ //";

    if (strlen($username) < $minLength || strlen($username) > $maxLength) {
        return false;
    }

    for ($i = 0; $i < strlen($username); $i++) {
        if (strpos($allowed_chars, $username[$i]) === false) {
            return false;
        }
    }

    return true;

}

$usernames = [
    "test",
    "test123",
    "test_123",
    "test.123",
    "test-123",
    "test\""
];

foreach ($usernames as $username) {
    echo "Username: $username is " . (validateUsername($username) ? "valid" : "invalid") . "<br>";
}
?>