How can I classify whether a software is a medium with the ability to grow into an enterprise level software or whether it is already there? And how should I use the information to choose the appropriate language/tool to create the software?

At first I was asking whether Java or PHP is the best tool to design enterprise level software, however I've suddenly realized that I am unable to put the software I'm tasked with redesigning into the proper scope so I'm lost.

Edit: I guess I'm looking for tell tale signs in software that may tip the favour towards enterprise level type software in the sense of functional and operational characteristics; functional: what it does (multi-functional), Architectural characteristics such as highly modular. operational: multi-sourced and multi-homed, databases, e.t.c. To be honest the reason I ask is because I'm skeptical about the use of PhP to design a piece of employee and partial accounting software. I'm more tipping towards the use of JSP and an hmvc framework such as JSF, wickets, e.t.c. where as the other guy wants to go the PhP way although I'm not experienced with PhP, as far as I know it's not an OO oriented language hence my skepticsm towards it.