Using Anonymous Functions (Closures) in PHP: Examples and Techniques

In PHP, anonymous functions (also called closures) allow you to define a function without a name, and they are most commonly used as callback parameters.

1. Referencing local variables inside an anonymous function (using the use keyword).

<?php
function F1(){
    $ok = "HelloWorld";
    $a = function() use ($ok) {
        echo "$ok";
    };
    $a();
}
F1();
?>

2. Placing an anonymous function inside a regular function.

<?php
function F1(){
    $a = function() {
        echo "HelloWorld";
    };
    $a();
}
F1();
?>

3. Returning an anonymous function from a regular function.

<?php
function F1(){
    $a = function() {
        echo "HelloWorld";
    };
    return $a;
}
$abc = F1();
$abc();
?>

4. Returning an anonymous function and passing parameters to it.

<?php
function F1(){
    $a = function($name, $do) {
        echo $name . " " . $do . " HelloWorld";
    };
    return $a;
}
$abc = F1();
$abc('张三', 'say');
?>

5. Using an anonymous function as a parameter to another function.

<?php
function F1($UnkownFun){
    $UnkownFun("张三");
}

F1(function ($username){
    echo $username;
});
?>