While trying to upgrade a customers installation to PHP 5.2.10 I learned that hard way that PEAR is broken in this release. This isn’t specific to any OS as the bug reports show but rather seems to be a general problem that slipped Q&A (who is laughing there?). All you’ll get is
"Cannot use a scalar value as an array in phar://install-pear-nozlib.phar/PEAR/ChannelFile.php on line 1391"
when trying to install PEAR.
So, for the time being, better not upgrade to PHP 5.2.10 if you need to use PEAR.