output caching

Hi All What is the best way to implement output chaching with PHP? I've only done a small amount of PHP work, I'm coming from a mostly ASP/ASP.NET background. In ASP.NET you can set a directive at the top of each script if the page should cache or not, how many seconds it shoudl be cached, and which combination of QueryString or HTTP Post variables it should consider when caching. Once cached, clients get served the output of the requested script, and the script is only executed once its expiration is reached. Is there a similar mechanism with PHP, or any sort of add-on? Thansk Brandon