What is the concept of PHP internal function

This article mainly introduces the relevant knowledge of "what is the concept of PHP internal function". The editor shows you the operation process through an actual case. The operation method is simple, fast and practical. I hope this article "what is the concept of PHP internal function" can help you solve the problem.

1. Concept

The function declared inside the function is the inner function.

2. Pay attention to use

(1) after calling the external function, you can call the internal function at will

(2) the internal function can be called within the function, but it must be called after the internal function definition, because the PHP parser will only load the external function and will not execute the external function, so it does not know that there are internal functions in the external function.

3. Examples

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