At ONJava.com, Jack Herrington writes:
"When the tag-line "Java scales and scripting languages don't" was born, it was based on EJB 1.0, an architecture that most Java architects would consider absurd, based on its high overhead. Based on EJB 1.0, Java's performance was much worse than that of scripting languages. It is only the addition of local interfaces in EJB 2.0 that makes the J2EE architecture perform well.
The argument for PHP scalability is further simplified, however, by the fact that both PHP and J2EE architecture (as well as others) are converging on the same design. And if "J2EE scales" given this simpler, logical three-tier architecture, then it follows that PHP does as well."