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:
<?php
function arithmetic($a, $b, $c) {
return $a($b, $c);
}
function add($b,$c){
return $b+$c;
}
$d = arithmetic('add', 5, 9);
echo '5 + 9 ='.$d;
?>Output result:
In addition, PHP provides two functionscall_user_func() and call_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, $param_arr is an index array, let’s take an example to see it in practice:
<?php
function arithmetic($f, $m, $n) {
return call_user_func_array($f, array($m, $n));
}
function add($m,$n){
return $m+$n;
}
$sum = arithmetic('add', 3, 4);
echo '3 + 4 ='.$sum;
?>Output result:
##call_user_func()
call_user_func ($callback [, $parameter, ... ])
," between multiple parameters. "separated. Let’s take an example to see it in action:
<?php
function arithmetic($f, $m, $n) {
return call_user_func($f, $m, $n);
}
function add($m,$n){
return $m+$n;
}
$sum = arithmetic('add', 250, 250);
echo '250 + 250 ='.$sum;
?>
<?php
function woziji($one,$two,$func){
//我规定：检查$func是否是函数，如果不是函数停止执行本段代码，返回false
if(!is_callable($func)){
return false;
}
//我把$one、$two相加，再把$one和$two传入$func这个函数中处理一次
//$func是一个变量函数，参见变量函数这一章
echo $one + $two + $func($one,$two);
}
//我们定义几个函数试试
function plusx2( $foo , $bar){
$result = ($foo+$bar)*2;
return $result;
}
function jian( $x , $y ){
$result = $x - $y;
return $result;
}
//调用一下函数，woziji，向里面传入参数试试
echo woziji(20,10,'plusx2');
//将plusx2改成jian试试结果
echo woziji(20,10,'jian');
?>
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