title: What are the disadvantages of using persistent connection in PDO
body: <p>In PDO, a connection can be made persistent using the <code>PDO::ATTR_PERSISTENT</code> attribute. According to the php manual - </p>
  
  <blockquote>
    <p>Persistent connections are not closed at the end of the script, but
    are cached and re-used when another script requests a connection using
    the same credentials. The persistent connection cache allows you to
    avoid the overhead of establishing a new connection every time a
    script needs to talk to a database, resulting in a faster web
    application.</p>
  </blockquote>
  
  <p>The manual also recommends not to use persistent connection while using PDO ODBC driver, because it may hamper the ODBC Connection Pooling process.</p>
  
  <p>So apparently there seems to be no drawbacks of using persistent connection in PDO, except in the last case. However., I would like to know if there is any other disadvantages of using this mechanism, i.e., a situation where this mechanism results in performance degradation or something like that.</p>