I got this error when trying to configure php 5.2.6:

configure: error: xml2-config not found. Please check your libxml2 installation.

I’m using Debian and it showed that I had libxml2 installed (and it was the latest version).

It turns out that the latest stable version of libxml2 doesn’t include a file named xml2-config. I suppose I could have linked that file to the config file that the stable version of libxml2 uses, but the easy fix is to just install the newer development version of libxml2 using the following command:

apt-get install libxml2-dev

That’s all I needed!