*sigh*
Ok, you're not getting it. On Oracle you get one and only one database per instance. So creating a new database in Oracle is NOTHING like creating a new database in most other databases where you can simply issue the CREATE DATABASE command.
Here is a example of what you need to do to create a new Oracle instance.
Creating an Oracle 10g database from the command line only
Now can you use PHP command line (perl/python/ruby/etc) to issue like commands? Sure you can. Would we want or try to? Heck no. Like anacedent said, use the right tool for the job.
Conversely, it's pretty easy to use PHP to create database objects (tables, views, indexes), which is probably what you and the folks saying you can create a database from PHP are talking about.