An upgrade to PHP5 using the Entropy package on my MacBook just tanked.
Turns out the fault is pretty basic.
If you’ve been running PHP already (i.e. you have already uncommented the lines in your httpd.conf file that allows PHP to run) then Apache can’t figure out which version of PHP to use and the install fails.
Simple solution – recomment those PHP lines.
E.g. #LoadModule php4_module libexec/httpd/libphp4.so