title: preg_replace: unknown modifier
body: <p>Let's assume that $body is equal to</p>
  
  <pre><code>something 
  that 
  does 
  not 
  interest 
  me 
  &lt;!-- start --&gt;
  some
  html
  code
  &lt;!-- end --&gt;
  something
  that
  does
  not
  interest
  me
  </code></pre>
  
  <p>If I use</p>
  
  <pre><code>$body=preg_replace("(.*)&lt;!-- start --&gt;(.*)&lt;!-- end --&gt;(.*)","$2",$body);
  </code></pre>
  
  <p>I obtain:</p>
  
  <blockquote>
    <p>Warning: preg_replace() [function.preg-replace]: Unknown modifier '&lt;' </p>
  </blockquote>
  
  <p>How have I to correct?</p>