Got this error when trying to add the mongodb stuff your php project – specially using composer then here is how to solve it.
The first thing is you have to add the mongodb driver to php.
You might need PEAR on your system. Adding pear to your system is relatively easy and google can help on that.
Then do the following on your terminal
sudo pecl install mongo
pecl install mongo
The last lines of successful installation would tell where the installation has occurred and some more important information.
Now you need to add the mongo.so to the php.ini
if you don’t know where you have php.ini run (on ubuntu)
echo "extension=mongo.so" >> path-to-php.ini