Method which allows only letters and whitespaces

Trying to create a method which allows only letters and whitespaces and deny everything that contains numbers and special symbols.

so here is the code

class Users{
    public $names = array();
    public function add($name){
    
    foreach($this->names as $key){
        if (preg_match("/[A-Za-z ]/", $key)) {
            array_push($this->names,$key);
            
        }else{
            unset($key);
        }
        }
    }
}

    $users = new Users();
    $users->add('Ja1ne');
    $users->add('Sara');
    $users->add('Chloe');
    $users->add(['Marty', '!Taylor', 'D3ndy']);
    var_dump($users);

it should output array with:Sara,Chloe,Marty