[smhg]

It was likely PHP 5. The last PHP 4 release is more than 10 years old [1].

Later versions of PHP 5 were worlds apart from version 4.

[1] http://php.net/supported-versions.php

[tombert]

I'm pretty sure it was 4, the company I was working for was...let's just say "slow to update", which is partly why I left.