Don't forget that Java also needs a very resource-hungry (and quite buggy and slow) runtime system.
From a maintenance point of view: every text editor can edit PHP files and the changes are active immediately. java must be compiled before it can be executed
And for the future, if you do it in java, it can only be maintained by someone who knows java. So you have to hire a java programmer, which are expensive/scarce. PHP is much easier to learn and thus much easier to maintain. (anyone who knows PERL knows PHP too)
One argument for java: it has a very rigid structure, it is very easy to make well-structured programs. PHP's loose structure lets you create crap scripts in no time at all. But then again, how good your scripts are depends on your qualities as a programmer, not on the language that you use.