The Perl vs PHP debate is meaningless.
Both execute about as fast as each other in the end.
It's all in the I/O.
A system using flat files will always execute slower than a system using an RDBMS.
Therefore, a Perl system using an RDBMS will outspeed a PHP system using flat files, and a PHP system using an RDBMS will outspeed a Perl system using flat files.
If you have speedy disk I/O, then chances are that your users will never notice the difference between the flat file system and the RDBMS system.