How to install/enable GMP (math functions) for PHP on Ubuntu?

When calling a gmp math function like gmp_mod, I get:

Fatal error: Call to undefined function gmp_mod()

I have installed the php5-gmp package and restarted the web-server, and the function is still undefined. The server is running Ubuntu 10.04 and PHP is running as an Apache module. All software was installed from official packages.

How do I enable the GMP math functions in PHP? I'm looking for a solution that uses official packages, not compiling from source.

Solution 1:

Here is the way which worked for me :

1. Installed GMP with apt-get install php5-gmp
2. Added extension=php_gmp.so to php.ini

Et voilà !

phpinfo() sample :

gmp
gmp support     enabled
GMP version     4.3.2 

It works fine here (Debian), so I suppose it will be ok for Ubuntu too.