This is here more for Perk's memory than anything else...When compiling PHP on a machine and attempting to enable mysql and mysqli, note that it works WAY better if you point right at the file you need.
EG:
./configure \
--with-apxs2=/usr/local/apache2/bin/apxs \
--with-mysql=/usr/local/mysql \
--with-pear \
--with-mysqli=/usr/local/mysql/bin/mysql_config \
--with-curl \
--disable-cgi \
--enable-ftp \
--enable-soap \
--enable-mbstring \
--enable-sockets \
--with-gd -with-png-dir=/usr \
--with-jpeg-dir=/usr \
--with-freetype-dir=/usr
as opposed to just
--with-mysql \
--with-mysqli \
Just sayin'.