I use both PHP and perl, mostly perl. The main things that I struggle with aren't so much the multitude of functions (that's no different than using CPAN modules), but really basic syntactic things. I can't tell you the number of times I've typed my $var='X'; in php when I've meant to say $var='X';. Another gotcha is the documentation. PHP is documented fairly well, but often the most useful bits of the documentation are often in the comments thread. Finally, the error messages can be a bit terse sometimes, you get used to that just like with any other language.