title: preg_replace or mb_ereg_replace in this case?
body: <p>I have this RegEx for matching whitespace in Unicode:</p>
  <pre><code>/^[\pZ\pC]+|[\pZ\pC]+$/u
  </code></pre>
  <p>I'm not even sure of what it does, but it seems to work. Now, in this case, which function applies better and why?</p>
  <pre><code>$str = preg_replace('/^[\pZ\pC]+|[\pZ\pC]+$/u', '', $str);
  </code></pre>
  <p>or</p>
  <pre><code>$str = mb_ereg_replace('/^[\pZ\pC]+|[\pZ\pC]+$/u', '', $str);
  </code></pre>