Cannot find config.m4 when installing eAccelerator

If you are following the instructions on this site:

http://developer.mindtouch.com/en/kb/Improve_PHP_performance_with_eAccelerator_on_Ubuntu_8.04_(Debian)

It is likely you're not in the correct directory. Go back to eaccelerator-0.9.5.3

cd /tmp/eaccelerator-0.9.5.3

then you should be able to run:

sudo phpize