Why php-mongodb extension fail to work?

Question

I find mongo.so mysql.so In my default extension dir /usr/lib/php5/20090626+lfs
Before they are all working well.
But today I have some update in my ubuntu,then mongo-extension fail to work in PHP.
But mongo.so is exist in the dir,and i add "extension=mongo.so" in /etc/php5/apache2/php.ini

Answer 1

I have solved it By adding a file named mongo.ini in /etc/php5/conf.d/
it's content is "extension=mongo.so"