Despite the fact that the PHP documentation team works around the clock to document the language and all its functions (and do a remarkably good job!), there are still some functions you will not find in the PHP manual. That is not to say they are unimportant, just that either very few people know how to use them, or that no one has had enough time to get around to them yet.
Although I have covered several of these functions in this book, there are probably many dozen more still around. Sometimes the only way to be certain is to look up the source code yourself.
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