title: When should I close database connection?
body: <p>I'm connecting to a MySQL database using<br></p>
  
  <pre><code>$dbh = new PDO("mysql:host=$db_host;dbname=$db_name", $db_user, $db_pass);
  </code></pre>
  
  <p>While reading through forums and tutorials it says that it is good practice (although not vital) to close a database connection as soon as you are finished with it. So my question is this: should I always add <code>$dbh = null;</code> when the last database operation has been executed?</p>