title: Use one bind_param() with variable number of input vars
body: <p>I try to use variable binding like this:</p>
  
  <pre><code>$stmt = $mysqli-&gt;prepare("UPDATE mytable SET myvar1=?, myvar2=... WHERE id = ?")) {
  $stmt-&gt;bind_param("ss...", $_POST['myvar1'], $_POST['myvar2']...);
  </code></pre>
  
  <p>but some of the $_POST['...'] might be empty so I don't want to update them in the DB.</p>
  
  <p>It's not practical to take into account all the different combination of empty $_POST['...'] and although I can build the string " UPDATE mytable SET..." to my needs, bind_param() is a different beast.</p>
  
  <p>I could try building its call as a string and use eval() on it but it doesn't feel right :(</p>