Ralph Schindler has a new post to his blog today detailing the process you'll need to compile Gearman (or just about anything) on a Zend Server CE install on Snow Leopard.
Zend Server CE for Mac (as of this writing), comes compiled as an i386 executable only. This includes the PHP binary, php library, and apache binaries that come shipped with ZSCE. While ZSCE works great out the box with all the provided extensions, you might find that you want some additional 3rd party PHP extensions compiled/linked into this stack. That's where things get a little confusing, and in this post, we'll look at how to install the gearman extension.
He give two methods - the easy way where you can export a CFLAGS setting to compile with multiple architectures or the harder way (that works for Gearman), building static libraries. The full list of commands (and some example output) is included in the post. In the comments there's also an example of the install if you're using Macports.