While tail'ing apache's error log is how I debug PHP as well, it is not nearly as nice as the possibility to get full debugging within PHP much like Python does.
Also, this would make it easier to use Xdebug or something like that as it wouldn't require that to be installed in a possibly production system.
Also, most beginners using PHP start off with some shared hosting somewhere and get the directory include stuff wrong and now have live bad code on the web. At my university that was a big issue, but it is the only way these beginners had to test their website.
for dumping arrays and things, i use an error_log_r() which just does print_r to the error log: