I’ve been trying to work out why the Zend Debugger wasn’t working from Zend Studio on one of our developer PC’s. We checked everything from the location of the plugin, php.ini, Apache config, comparing this with a Linux box where it seems to work fine. After pulling my hair out and spending some time on Google I found that this is a known issue which hopefully Zend will be fixing soon. In the meantime you can work around this by forcing Apache back into 32-bit mode as follows:

1. Stop Apache HTTP

sudo apachectl stop

2. Restart it in 32-bit mode

sudo arch -386 /usr/sbin/httpd

It then works perfectly.