Quickly repair memcached installed but not found on apache server (debian)

I have a debian server with php installed and working from several year, today I recevied an error about memcached, I tried un installing and reinstalling but now it is not working anymore I have :

Uncaught Error: Class "Memcached" not found

Memcached and php-memcached are installed, I really don't understand.
I need an immediate solving. Thanks