cleen catch data, post or get

carch_data.php

$clean = array();
switch($_POST['color']) {
  case 'red':
  case 'green':
  case 'blue'
    $clean['color'] = $_POST['color'];
    
  default:  /*ERROR*/
    break;
}

/*numere si liter*/
$clean = array();
$length = mb_strlen($_POST['username']);
if (ctype_alnum($_POST['username']) && ($length > 0) && ($length <= 32)) {
$clean['username'] = $_POST['username'];
}
else {
/* ERROR */
}

/*expresii regulate*/
$clean = array();
if (preg_match('/[^A-Za-z \'\-]/', $_POST['last_name'])) {
/* ERROR */
}
else {
$clean['last_name'] = $_POST['last_name'];
}

/*XSS*/
$html = array(
'username' => htmlentities($_POST['username'], ENT_QUOTES, 'UTF-8'),
);
echo $html['username'];