I have reasonable knowledge of PHP, Perl, and Bash. I use Perl for most text processing on my system (find, replace, filter output, etc). I use PHP for web development, allowing a user to view and interact with database data via the browser. I use Bash for quick and dirty scripts often to supplement the more complex Perl scripts.
I'm a big believer of focusing on as few languages as possible (to get the job done) and becoming an expert in them.
So the question is, why not use PHP for the common tasks that Perl (and Bash) are used? Are there good reasons (limitations or features) why PHP is mostly used for web development, while Perl and Bash are mostly used for "offline" "scripting"?