title: Difference between ob_clean and ob_flush?
body: <p>What's the difference between <code>ob_clean()</code> and <code>ob_flush()</code>?</p>
  
  <p>Also what's the difference between <code>ob_end_clean()</code> and <code>ob_end_flush()</code>? I know <code>ob_get_clean()</code> and <code>ob_get_flush()</code> both get the contents and end output buffering.</p>