We have a web server (Debian, with Apache2, PHP4 and MySQL) used in an Intranet. It's main use is to serve pages with data and graphs generated dynamically (using jpgraph) from the data stored in DB.
It has worked rock solid for several years, but this week we have found that everything related to graphs is not working. This includes jpgraph and gnuplot generated figures, both dependent on library gd. Also there are no references to "gd" in phpinfo(), and any direct call to gd functions (like gd_info()) results in an error.
We have tried to reinstall php4-gd (and restarting Apache) with no result. Obviously we have done something wrong, but we cannot figure out what it is.
What can we have done? Is there any other diagnosis we can do to isolate the problem?