How to create a Hashcash in PHP
<p>After searching the Web, I couldn't find an answer on how to create a hashcode in php.</p>

<p>I'm writing a Newsletter-Tool and don't wan't to get blacklisted, ok who wants :-)</p>

<p>I have already checked my reverse DNS, SPF an spamhouse.org...</p>

<p>Can someone help me out on how to create a hashcash in PHP (with example)?</p>
