Not allow alt codes in register

[Lasers]

How do I not allow people to make usernames with alt codes in them?

[MentaL]

[Alexus54321]

if (preg_match("/^[a-zA-Z0-9._]{3,15}$/", $username)) {

[...]

} else {
$msg = 'There are invalid characters in your username, please check it!';
}

Something like this maybe?

OR

$filter = preg_replace("/[^a-z\d\-=\?!@:\.]/i", "", $name);

[...]

}elseif($filter !== $name){
$msg = "The special characters are disabled.";

Greez,

[Lasers]

if (preg_match("/^[a-zA-Z0-9._]{3,15}$/", $username)) {

[...]

} else {
$msg = 'There are invalid characters in your username, please check it!';
}

Something like this maybe?

OR

$filter = preg_replace("/[^a-z\d\-=\?!@:\.]/i", "", $name);

[...]

}elseif($filter !== $name){
$msg = "The special characters are disabled.";

Greez,

When i add that in my register page just says "Server Error 500"

[Troll Hotel]

Because you have to edit it..
can you post your register please ;p

[Vimsoration]

Here i have made a fast code for you:

$filter = preg_replace("/[^a-z\d\-=\?!@:\_]/i", "", $name); 

This is the best way to secure it.