IMHO, once you know perl, it's easy to learn and use PHP proficiently. You'll need to keep php.net close at hand for all of the myriad functions you have at your disposal, but I think that's no big hardship.

As far as which language is best for the project, it seems like your project would be just fine for PHP. Also, it seems small enough that it would give you a good opportunity to learn PHP and increase your "bankability" :-)

If you have control over the systems where the application will be installed then it's a wash I think as to which language you should use. For a perl implementation you'll need to install some modules to interact with mysql. That's often a difficulty on systems where you have no control. For a PHP implementation, it usually comes with everything (including the kitchen sink) that you'll need so no extra installation.

Oh, and as others have said as far as the languages go, perl and php are equally secure. It's all in how you write your code (and for php, in how you configure it).