Learning curve
PHP is easy to learn, fast to deploy.
typical J2EE developer needs to read 1000’s of pages about various web frames works, template engines to make choice and do perfect deployment. Few people have that patience.
Even though Ruby’s dynamic typing, it’s easy than Java.

Scalability / Availability
PHP can run on all the Dedicated Server, VPS, Shared host.
Java and Ruby rarely can run on Shared host.

Development Speed
Development speed on Ruby on Rails is fastest.
PHP also has some quick development framework such as CakePHP.
Java is the slowest.

Maintainability
Java and Ruby have good maintainability.
PHP script is a bit hard to maintenance.