What three types of php functions can be divided into

1. Variable function

Variable function is also called variable function. When the php script is executed, it will look for a function with the same name as the value of the variable. And execute it. The advantage of this is that you can assign different function names to the same variable, assign that function name to the variable, and use the variable name plus parentheses in the program to call that function for execution.

2. Recursive function

The recursive function is also called a self-calling function. It will call itself during the execution process. Generally, conditions will be attached to determine whether the recursive call needs to be executed. Under certain conditions The call will be terminated and the process control will be returned to the upper layer function for execution. If there are no additional conditions in the recursive function, the program will loop infinitely and cause an error.

The biggest advantage of recursive function calling is that it can simplify the complex and repeated calling procedures in the program. This feature can be used to perform complex operations. Non-recursive functions are efficient. But it is more difficult to program. Moreover, it is less readable and does not meet the current programming goals. In short, it encourages the idea of ​​using recursive functions to implement programs.

3. Custom functions

php provides us with a huge function library for us to use. The function library is a design pattern in programming, and functions are structures. Designed modules. Functions can be used in multiple files in the same project, and functions are usually organized into one file or multiple files.

If you use a function defined in a function library in PHP, you need to use one of include(), include_once(), require or require_once to load the function library file into the program.

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