试了不少方法，最后还是这个最有效。
[转自：http://thatsimplecode.com/install-mongodb-driver-for-php-on-xampp-for-mac-osx]
You need to have the following installed in your Mac:
Type the following in your terminal :
brew install wget
brew install autoconf
sudo /Applications/XAMPP/xamppfiles/bin/pecl install mongo
Add extension=mongo.so to your php.ini file
which can be found
at /Applications/XAMPP/xamppfiles/etc by
default.
Restart Apache.
A..nd you are done.
Tip:
To install MongoDB, you can use
brew install mongodb Install MongoDB driver for PHP on XAMPP for Mac OSX,布布扣,bubuko.com
Install MongoDB driver for PHP on XAMPP for Mac OSX
原文：http://www.cnblogs.com/wf225/p/3733606.html