use sudo apt-get install php5-mongo you will have it working.hope it helps :)
sudo apt-get install php5-mongo
Install your mongo.so in your lampp
/opt/lampp/lib/php/extensions/
Keep this path in your
/opt/lampp/lib/php/php.ini file
extension=mongo.so
try this
if that doesnt work try thesesudo apt-get install php5-dev make php-pearsudo pecl install mongosudo echo "extension=mongo.so" | sudo tee /etc/php5/mods-available/mongo.ini