Recently I installed bugzilla (developed in php). Its pretty amazing what people can create considering all were volunteers.

First I tried to install in windows, eventually gave up as the DB driver was not installing and had a whole bunch of compiling issues. Then installed on ubuntu after lot of bumps - I had to go all over the internet to troubleshoot lot of major / minor issues.

It seems lot of hard work went into php earlier (bugzilla needs a lot of modules) but now people are moving on to newer stuff.