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Christopher Wehkamp1,494 Points
What are "internal functions" and how does (is_array($arr) work?
Hampton glazes right over this like we have already covered it, but this has never been referenced in the previous PHP videos of the PHP track.
What is an internal function? How is it different from other functions?
What does the function is_array() do? How does it do what it does?
Are there presumably many other internal functions like is_integer() or is_boolean() which perform checks on datatypes in the same way?
Simon Coates28,693 Points
internal functions are functions that are defined by php. you get these for free. The documentation for is_array is here. Yest, there are a bunch of similar functions for the other datatypes.