I have a mac with a custom PHP 5 install that built from about a year ago. I remember it took all Sunday and I had to compile about 20 times to get it right. The MySQL I have is
FYI; the MySQL PDO driver is included in the php 5.2.9 and 5.3 builds from Marc Liyanage's entropy.ch
You're going to need to compile it by hand, instead of via PECL. You'll need to know where your MySQL install is. I don’t know about the Entropy packages, but the builds provided by MySQL (which I recommend) install into /usr/local/mysql
.
$ pecl download pdo_mysql
$ tar xzf PDO_MYSQL-1.0.2.tgz
$ cd PDO_MYSQL-1.0.2
$ phpize
$ ./configure --with-pdo-mysql=/usr/local/mysql
$ make && sudo make install
And that should get you to the point where you can configure it.