How to use PHP callback functions (detailed examples)

In the previous article, I brought you "How to play with PHP custom functions (summary sharing)". This article introduces the custom functions in PHP in detail. This article This article takes a look at the basic callback functions in PHP functions. I hope to be helpful!

PHP callback function

Callback function, a function structure that can cooperate with anonymous functions and variable functions to achieve more functions .

What is a callback function?

The callback function in PHP actually means that when calling a function, instead of passing standard variables to the function as parameters, another function is passed as a parameter to the called function. The callback function is the function that takes the parameter.

It can be understood that the callback function is also a function we defined, but it is not called directly, but requires another function to be called.

The example is as follows:

Output result:

In addition, PHP provides two functionscall_user_func()andcall_user_func_array()to support callback functions.

The difference between these two functions is: call_user_func_array() receives the parameters of the callback function in the form of an array, while call_user_func() receives the parameters of the callback function in the form of specific parameters.

• call_user_func_array()

The call_user_func_array function can call the callback function and then use an array as the parameter of the callback function . The syntax format is as follows:

call_user_func_array ($callback ,$param_arr)

In the syntax format, $callback is the called callback function, $param_arr is an index array, let’s take an example to see it in practice:

Output result:

• ##call_user_func()

call_user_func ($callback [, $parameter, ... ])

," between multiple parameters."separated. Let’s take an example to see it in action:

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