使用php和regex从字符串中删除数字和特殊字符[复制]

I have some problems with removing numbers and special characters. I want to remove all numbers and special characters from the input. Here's my code :

$input = $_POST["input"];

function preprocessing($input){
    $input = trim(strtolower($input));
    $remove = '/[^a-zA-Z0-9]/s';
    $result = preg_split($remove, $input, -1, PREG_SPLIT_NO_EMPTY);
    for($i = 0; $i < count($resultl); $i++){
        $result[$i] = trim($result[$i]);
    }
    return $result;
}

String example : qwd qwd qwdqd123 13#$%^&*) ADDA ''''

Output : Array ( [0] => qwd [1] => qwd [2] => qwdqd123 [3] => 13 [4] => adda )

The numbers still appear on my string. How to solve this ? Thank you before.

</div>

Check this

function clean($string) {
   $string = str_replace(' ', '-', $string); // Replaces all spaces with hyphens.

   return preg_replace('/[^A-Za-z\-]/', '', $string); // Removes special chars.
}