anonymous function and Closure (closure) usage in PHP

This article mainly introduces the anonymous function and the closure (closure) usage in PHP, and I hope it will help you with your friends ' reference.

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

$closureFunc = function ($str) {echo $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 () {    $func = function () {        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 = ClosureFunc3 (); function returns the 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.

function ClosureFunc4 () {    $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?

function ClosureFunc5 () {    $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

function ClosureFunc5 () {    $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

Related recommendations:

Knowledge about JavaScript closures and how to use them

JS Closure use detailed

A deep understanding of the Python closure mechanism