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:

• MongoDB
• XAMPP for Mac OSX
• Homebrew Package Manager

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