Need some help about using Boost.PHP to make extensions

Hi all, it's been a while since my last thread. I've been playing around with Boost.PHP these days, and find it pretty much satisfactory. Now, I need some help on how Boost.PHP treat with PHP arrays. Not complaining, but there isn't much document I can learn from the official website. And if this thread is NOT totally about PHP, I'm sorry about this. This mailing list is the only place possibly I can find answers about it. I can't find a suitable C/C++ forum to ask this question since they don't work with PHP though. :( I'm trying to get an array('key'=>'val') (associative array) as argument, and return a std::string of 'key:val' back to PHP. Now, I can get the keys but not the arrays. I thought there might be something wrong with how I was using php::array::const_reference. Can anyone be so kind to explain how it works? Or perhaps a piece of working code that I can learn about? Thank you!