Match determined char between chars

Match determined char between chars

I have the following code:
<?php
<div>
<p>some text</p>
<code>
<span>some code</span>
</code>
<p>another text</p>
<code>
<span>another code</span>
</code>
</div>
?>
All the code is a string.
I want some REGEX to match all "<", but only those which is surrounded by
<code></code>.
I tried a lot and made a lot of research in internet and failed to find
some REGEX that matches it. I'm not good with REGEX yet. Can someone help
me, plz?
Thx a lot!