Anonymous functions and closure usage in php

This article mainly introduces the usage of anonymous functions and closures in php. Interested friends can refer to it. I hope it will be helpful to everyone.

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

Anonymous functions (Anonymous functions) in php, also called Closure function (closures) allows specifying a function without a name. The most commonly used one is the parameter value of the callback function. (http://php.net/manual/zh/functions.anonymous.php)

Definition of anonymous function:

$closureFunc = function(){

　　　　....

 };

eg : Assign the anonymous function to a variable and call it through the variable

 $closureFunc = function($str){

　　 echo $str;

  };  $closureFunc("hello world!");

Output: hello world !

2: Closure

2.1 Put the anonymous function in the ordinary function, you can also put the anonymous function Return, this constitutes a simple closure

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

##2.2 Reference local variables in anonymous functions

##

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

After the above function is run, it will A Notice error is 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

 2.3  返回匿名函数

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

2.4 当我们在返回匿名函数时候怎么给匿名函数传参呢？ 其实跟普通函数传参数一样

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

2.5 怎么用闭包来改变上下文引用的变量值？

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

看上面的输入结果，显然没有达到目的， 其实只要加一个 & 引用符号就可以了

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

2.6 把匿名函数当作参数传递

function callFunc($func){    $func("argv");
}

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

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