title: replace urls in string preg_replace regex php
body: <p>I need to replace urls in my content with another url prefix: 
  i.e. if the current url is <code>&lt;a href="http://myoldurl.com"&gt;link&lt;/a&gt;</code> and I want to change it to:
  <code>&lt;a href="http://myurl.com/create/?url=http://myoldurl.com"&gt;link&lt;/a&gt;</code> how can replace my links using preg_replace?</p>