Check this site out for a comparison of the various module counts per language. It is really incredible that rubygems surpassed CPAN last year and continues to grow at a very rapid rate. Quality may be another matter, but still, impressive.
The closest PHP has to CPAN is PEAR (http://pear.php.net). It stalled for a long time, although development seems to have picked up a bit now that everything is on GitHub (https://github.com/pear/)
http://www.modulecounts.com/