title: How to enable whitespace insensitive mode of regular expression in PHP?
body: <p>I've tried "m" modifier,but not working:</p>
  
  <pre><code>$reg = '/...
          /m';
  
  preg_match($reg,...,$match);
  </code></pre>
  
  <p><strong>EDIT</strong></p>
  
  <p>Or maybe I need a modifier that can ignore white space like ENTER,TAB and so on.
  Because when I remove the white space in my regex it works.</p>
  
  <p><strong>EDIT AGAIN</strong>:</p>
  
  <p>I need a modifier so that regular expression </p>
  
  <pre><code>"/aaaa b/",
  "/aaaa
   b/"
  </code></pre>
  
  <p>are the same thing,say,it just ignores the white space in regex itself.</p>