Since etch php is compiled with large file support. This breaks binary compatibility to other packages, which are commonly not compiled with LFS and leads into trouble with 3rd party extensions, cause these are precompiled against the ABI of upstream and LFS not turned on. One example is Zend Optimizer. You may say this will only hit closed source applications, but if these are customer requirements, you have to solve the issue in some way.
You can do this by compiling your php and all extension from source without LFS enabled, but here you have to care about bugs, regressions and exploits for your own.
An other solution is to rebuild the packages from etch with LFS disabled. I've done this with the source packages of php4 and php5 from etch. Additionally I did backport php-suhosin from unstable against this php packages for php4 and php5.
Packages are available at http://ftp.cyconet.org/debian/archive/special/ or via
deb http://ftp.cyconet.org/debian etch-special-cyconet main non-free contrib
If there are any DSA popping up, you can expect updates with a short delay. Please keep in mind, that you cant install php extension directly from etch. You need to rebuild them against php-dev with disabled LFS. Other php packages may appear later.
Update: We migrated a customer system with Zend Optimizer to etch. To my surprise, it was working with latest version of Zend Optimizer out of the box with php4. Can't say anything for php5, cause there are some modifications needed, until the applications are working with php5.
Maybe anybody can verify this with php5?
Until all works well with stock php, I wont maintain the packages mentioned above.