PHP: Anonymous function (closure) [i]

Excerpt from: http://www.cnblogs.com/starlion/p/3894578.html

One: anonymous function (Can be used at php5.3.0 or above)

The anonymous function in PHP (Anonymous functions), also called the closure function (closures), allows you to specify a function without a name. The most common is the parameter value of the callback function. (http://php.net/manual/zh/functions.anonymous.php)

Definition of anonymous function:

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

Eg: assigning an anonymous function to a variable and invoking it through a variable

$closureFunc function ($strecho$str;  };   $closureFunc ("Hello world!");

Output: Hello world!

Two: Closures

2.1 The anonymous function in the normal function, or the anonymous function can be returned, which constitutes a simple closure

function closureFunc1 () {    $funcfunction() {        echo "Hello";    };     $func();} ClosureFunc1 (); // Output: Hello

2.2 referencing local variables in anonymous functions

function ClosureFunc2 () {    $num = 1;     $func function () {        echo$num;    };     $func ();} ClosureFunc2 (); // notice:undefined Variable:num

After the above function runs, it will report notice error, indicating that we can not use the local variables in the anonymous function, it is necessary to refer to a PHP keyword used, the code is as follows

function ClosureFunc2 () {    $num = 1;     $func function  Use ($num) {        echo$num;    };     $func ();} ClosureFunc2 (); // Output: 1

2.3 Returning anonymous functions

function closureFunc3 () {    $num = 1;     $func function  Use ($num) {        echo$num;    };     return $func ;} $func // function returns anonymous function $func // then we are using $func ()//output: 1

2.4 How do we pass an anonymous function to an anonymous function when we return it? In fact, as with normal function arguments.

functionClosureFunc4 () {$num= 1; $func=function($str) Use($num){        Echo $num; Echo"\ n"; Echo $str;    }; return $func;}$func=ClosureFunc4 ();$func("Hello, Closure4");//output://1//hello, Closure4

2.5 How do I use closures to change the value of a context-referenced variable?

functionClosureFunc5 () {$num= 1; $func=function() Use($num) {        Echo"\ n"; $num++; Echo $num;    }; Echo"\ n"; Echo $num; return $func;}$func=ClosureFunc5 ();$func();$func();$func();//output://1//2//2//2

Look at the above input results, obviously did not achieve the purpose, in fact, just add a & quote symbol can be

functionClosureFunc5 () {$num= 2; $func=function() Use(&$num) {        Echo"\ n"; $num++; Echo $num;    }; Echo"\ n"; Echo $num; return $func;}$func=ClosureFunc5 ();$func();$func();$func();//output://2//3//4//5

2.6 Passing anonymous functions as parameters

function callfunc ($func) {    $func("argv");} Callfunc (function($str) {    echo$str;}) // output://argv

Reference:

Http://www.cnblogs.com/yjf512/archive/2012/10/29/2744702.html why to introduce closures

http://blog.csdn.net/lgg201/article/details/6127564 php 5.3.0 function () use () {}

PHP: Anonymous function (closure) [i]