title: PHP- PDO Only variables should be passed by reference
body: <p>When i try to Register on my website this error appears Strict standards: Only variables should be passed by reference. Can you see what is wrong with my code?</p>
  
  <p><img src="https://i.stack.imgur.com/H19TW.png" alt="enter image description here"></p>
  
  <pre><code> public static function create(user $user){
          $conn= DataBase::getDB();
  
          $stmt=$conn-&gt;prepare("INSERT INTO `institute`.`user` (`id`, `name`, `surname`, `username`, `password`, `email`, `registration_number`) "
                  . "VALUES ('', :name, :surname, :username, :password, :email, :registration_number)");
  
          $stmt-&gt;bindParam(':name', $user-&gt;getName());
          $stmt-&gt;bindParam(':surname', $user-&gt;getSurname());
          $stmt-&gt;bindParam(':username', $user-&gt;getUsername());
          $stmt-&gt;bindParam(':password', $user-&gt;getpassword());
          $stmt-&gt;bindParam(':email', $user-&gt;getEmail());
          $stmt-&gt;bindParam(':registration_number', $user-&gt;getRegistration_number());
  
  
  
         $stmt-&gt;execute();
  
      }
  </code></pre>