Detailed explanation of anonymous functions and closure examples in php-PHP Tutorial-php.cn

1: Anonymous function

The anonymous function in php, also called the closure function, allows you to specify a function without a name. The most commonly used one is the parameter value of the callback function.

Definition of anonymous function:

$closureFunc = function(){　　　　.... }; eg: 把匿名函数赋值给变量，通过变量来调用 $closureFunc = function($str){　　 echo $str; }; $closureFunc("hello world!"); 输出： hello world!

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2: Closure

2.1 Put 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

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2.2 Referring to local variables in anonymous functions

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

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After the above function is run, A Notice error will be reported, indicating that we cannot use local variables in anonymous functions. At this time, we need to quote a PHP keyword use. The code is as follows

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

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2.3 Return to 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

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2.4 How 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

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2.5 How to use closures to change the variable values 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

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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

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2.6 Pass anonymous functions as parameters

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

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