php Using if is not changing wtf?

If the $status = pending or success the result is always warning. How is that possible? Am I using the else right? Maybe someone can help me with it. The $status is coming from a database. Can you explain whats the difference between = and == ?

Thanks sincerely Dennis

<?php if ($status == "pending") { 
            $class ="warning";
      } else if ($status == "succes"){
            $class = "succes";
      }
?>