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It also hanged the tab several times during the test.

Downvoted because the user didn't provide a link to the PHP manual (I only found one that was 28.5MB, which used ~200MB on Opera 9.52 (judged by the difference in Task Manager), but loaded relatively quickly and was scrollable, searchable the whole time). Also didn't mention how much memory Firefox consumed to show the page, to compare.

I was using PHP 5.0 manual downloaded about 6 months back from their site. I can post it to you if you give your email address :)

In Firefox it is hard to know exactly the memory consumption per tab. With 50 other tabs open in Firefox as well as the page mentioned it is conmsuming 33 MB only! This is real folks. Just try it out and you will realize the problems are serious.

Other users have confirmed the memory issues too in the comments on the post.