What exactly is the difference between the is_callable and function_exists in PHP?

Question

I am working on a project, in which I am using a deprecated function from the older version. But don\'t want my script to stop if used in the older version.

So I am check

Answer 1

When used with a function (not a class method) there is no difference except that function_exists is slightly faster.

But when used to check the existence of methods in a class you cannot use function_exists. You'll have to use is_callable or method_exists.