As David Soria Parra mentions in a recent post to his blog, the DTrace functionality has been backported to the PHP 5.3 branch and gives developers a bit more information about what's happening inside their applications.

For those not following the PHP development. We backported the DTraces probes from the abandoned PHP 6.0 branch, back to the new trunk PHP 5.3.99-dev. It is called 5.3.99 because the PHP dev community has not decided yet on a version number (5.4 or 6.0).

He gives the configure line to get it working on Solaris and Mac OSX and a sample line of code to ensure everything's working correctly. The results show the full execution of the example. This functionality can replace this extension from the PECL repository.