PHP is not a fully-featured language like Perl so you might miss out on something you find standard in Perl. Also, considering speed, Perl will often beat PHP in comparable matches which usually will involve mod_perl or fastcgi since a generic CGI is not a fair comparison. Plus, with Perl you get great support, FOR FREE! Don't believe me? Check out
PHPmonks.org. Aw! Dead link? Sorry. Perl has far more many general purpose and useful modules available all in one
place. For example, try to find the useful, well-reviewed
Bone::Easy module for PHP. It ain't gonna happen, folks. Anyway, I see CGI as a wrapper for HTML not vice versa as in PHP.