การต่อ sql

$sqlall = "SELECT users.id, users.firstname, users.lastname, users.phone
            FROM users
            WHERE users.id IS NOT NULL";

if(isset($_POST['srchtext'])){
  $search = $_POST['srchtext'];
  $sqlall .= " AND (
    users.firstname LIKE '%$search%'
    OR users.lastname LIKE '%$search%'
    OR users.phone LIKE '%$search%'
  )";
}