How to check for white spaces and special characters - php

Question

I am trying to code a form for a login using php to check it. But I can't get it to check the if I have any whitespaces and special characters for the username. I tried using the [\W]+ but that did not work.
<?php
$usernerr = "";
$passwerr = "";
$usern = "";
$passw = "";
$pattern = '/[\'\/~`\!##\$%\^&\*\(\)_\-\+=\{\}\[\]\|;:"\<\>,\.\?\\\]/';
if($_SERVER['REQUEST_METHOD'] == 'POST')
{
if(empty($_POST['uname']))
{
$usernerr = "*Please add a username please!";
}
else
{
$usern = clearInput($_POST['uname']);
if(!preg_match('/s/', $usern) || !preg_match($pattern, $usern))
{
$usernerr = "*Username have only letters and numbers!";
}
$usernerr = "";
}
if(empty($_POST['psw']))
{
$passwerr = "*Please add a password please!";
}
else
{
$passw = clearInput($_POST['psw']);
$passwerr = "";
}
}
function clearInput($input)
{
$input = trim($input);
$input = stripslashes($input);
$input = htmlspecialchars($input);
return $input;
}
?>

Answer 1

Considering the error message you wrote, you are complicating yourself.
Instead of searching for the list of characters that aren't alpha num, search for alpha num only. Try using this pattern, and don't negate the condition.
$pattern = "/^[a-zA-Z0-9]+$/";
// Some code...
if(preg_match($pattern, $usern))
// ^-------------------------------Notice the changes
{
//Username is valid
}
Description of the pattern :
^ from the begining
[a-zA-Z0-9] search an alpha num
+ 1 or more time
$ to the end
/^[a-zA-Z0-9]+$/can be replaced by /^[[:alnum:]]+$/ or /^[a-z\d]+$/i which produce the same effect.