Anonymous functions and closures in php

1:Anonymous functions(can only be used in php5.3.0 or above)

Anonymous functions in php (Anonymous functions) , also called closure function (closures), allows you to specify a function without a name. The most commonly used one is the parametervalue of the callbackfunction.

Definition of anonymous function:

$closureFunc = function(){ 　　　　.... };

eg: Assign the anonymous function to thevariableand call it through the variable

$closureFunc = function($str){ 　　 echo $str; }; $closureFunc("hello world!");

Output: hello world!

2: Closure

2.1Put the anonymous function in a normal function, or you can return the anonymous function, which constitutes a simple Closure

function closureFunc1(){ $func = function(){ echo "hello"; }; $func(); } closureFunc1();//输出: hello

2.2In the anonymous functionReferencelocal variable

function closureFunc2(){ $num = 1; $func = function(){ echo $num; }; $func(); } closureFunc2();//Notice: Undefined variable: num

After the above function is run, a Notice error will be reported, indicating that we Local variables cannot be used in anonymous functions. At this time, a PHP keyword use must be quoted. The code is as follows

function closureFunc2(){ $num = 1; $func = function() use($num){ echo $num; }; $func(); } closureFunc2();//输出: 1

2.3Return anonymous function

function closureFunc3(){ $num = 1; $func = function() use($num){ echo $num; }; return $func; }$func = closureFunc3(); //函数返回匿名函数$func(); //然后我们在用$func() 调用//输出: 1

2.4How do we pass parameters to the anonymous function when we return it? In fact, it is the same as passing parameters to a normal function.

function closureFunc4(){ $num = 1; $func = function($str) use($num){ echo $num; echo "\n"; echo $str; }; return $func; }$func = closureFunc4();$func("hello, closure4");//输出: //1 //hello, closure4

2.5How to use closure to change the variable value referenced by the context?

function closureFunc5(){ $num = 1; $func = function() use($num) { echo "\n"; $num++; echo $num; }; echo "\n"; echo $num; return $func; }$func = closureFunc5();$func();$func();$func();//输出: // 1 // 2 // 2 // 2

Looking at the above input results, it is obvious that the purpose has not been achieved. In fact, just add an & reference symbol.

function closureFunc5(){ $num = 2; $func = function() use(&$num) { echo "\n"; $num++; echo $num; }; echo "\n"; echo $num; return $func; }$func = closureFunc5();$func();$func();$func();//输出: // 2 // 3 // 4 // 5

2.6Pass anonymous functions as parameters

function callFunc($func){ $func("argv"); } callFunc(function($str){ echo $str; })//输出： // argv

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