Monitor assignment PHP extension

I'm trying to figure out if it is possible to make an extension that monitors every assignment that is made in PHP.

I want to do some taint detection, I've seen the PHP taint project, but it would be nicer to have it as an extension for my project.

Additionally, where can I find API documentation and similar for Zend/PHP extensions, I haven't been able to find anything good开发者_如何学Python :/

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http://pecl.php.net/package/taint