Setup Yii on built in MacOS 10.6 Apache


I tried to run yii sample on my macbook pro running MacOS 10.6 Snow Leopard. I activated Apache and PHP. Put extracted yii folder on my $HOME/Site. Try access it using my public Sites display none. I moved the yii folder to /Library/WebServer/Documents. I change the ownership and group to _www. I got this error

Error 500

Application runtime path "/Library/WebServer/Documents/yii/demos/blog/protected/runtime" is not valid. Please make sure it is a directory writable by the Web server process.

I tried to chmod 777 on protected/runtime. But error message still appear. What should I do with this?

Thanks a lot.