title: PHP - Issue with PDO when using concat
body: <p>I have the following code which does not work and i don't understand why.</p>
  
  <p>Could anybody help me with PDO's subtleties ?</p>
  
  <pre><code>&lt;?php
  
  $stmt = $con-&gt;prepare("SELECT DISTINCT title FROM articles WHERE concat(id,'-',value) IN (?)");
  $stmt-&gt;bindParam(1, $concat);
  
  //Works
  $concat = "1-4";
  $stmt-&gt;execute();
  $results = $stmt-&gt;fetchAll();
  var_dump($results);
  
  //Does not work
  $concat = "'1-4','1-5'";
  $stmt-&gt;execute();
  $results = $stmt-&gt;fetchAll();
  var_dump($results);
  </code></pre>
  
  <p>Thank you :)</p>