解析PHP閉包及Clourse類別方法的作用

<?php
$hello = function ($word) {
    return &#39;hello &#39; . $word;
};
echo $hello(&#39;world&#39;);
// 输出 hello world

<?php
$name = &#39;panda&#39;;
$hello = function () use ($name) {
    return &#39;hello &#39; . $name;
};
echo $hello();
// 输出 hello panda

<?php
$name = &#39;panda&#39;;
$hello = function () use ($name) {
    return &#39;hello &#39; . $name;
};
$name = &#39;cat&#39;;
echo $hello();
// 输出 hello panda

<?php
$name = &#39;panda&#39;;
$changeName = function () use (&$name) {
    $name = &#39;cat&#39;;
};
$changeName();
echo $name;
// 输出 cat

<?php
class Dog {
    public $name = &#39;Wang Cai&#39;;
}
$dog = new Dog();
$changeName = function () use ($dog) {
    $dog->name = &#39;Lai Fu&#39;;
};
$changeName();
echo $dog->name;
// 输出 Lai Fu

<?php
$clourse = function () {
    echo &#39;hello clourse&#39;;
};
if (is_object($clourse)) {
    echo get_class($clourse);
}
// 输出 Closure

/**
 * Class used to represent anonymous functions.
 * <p>Anonymous functions, implemented in PHP 5.3, yield objects of this type.
 * This fact used to be considered an implementation detail, but it can now be relied upon.
 * Starting with PHP 5.4, this class has methods that allow further control of the anonymous function after it has been created.
 * <p>Besides the methods listed here, this class also has an __invoke method.
 * This is for consistency with other classes that implement calling magic, as this method is not used for calling the function.
 * @link http://www.php.net/manual/en/class.closure.php
 */
final class Closure {
    /**
     * This method exists only to disallow instantiation of the Closure class.
     * Objects of this class are created in the fashion described on the anonymous functions page.
     * @link http://www.php.net/manual/en/closure.construct.php
     */
    private function __construct() { }
    /**
     * This is for consistency with other classes that implement calling magic,
     * as this method is not used for calling the function.
     * @param mixed $_ [optional]
     * @return mixed
     * @link http://www.php.net/manual/en/class.closure.php
     */
    public function __invoke(...$_) { }
    /**
     * Duplicates the closure with a new bound object and class scope
     * @link http://www.php.net/manual/en/closure.bindto.php
     * @param object $newthis The object to which the given anonymous function should be bound, or NULL for the closure to be unbound.
     * @param mixed $newscope The class scope to which associate the closure is to be associated, or &#39;static&#39; to keep the current one.
     * If an object is given, the type of the object will be used instead.
     * This determines the visibility of protected and private methods of the bound object.
     * @return Closure Returns the newly created Closure object or FALSE on failure
     */
    function bindTo($newthis, $newscope = &#39;static&#39;) { }
    /**
     * This method is a static version of Closure::bindTo().
     * See the documentation of that method for more information.
     * @static
     * @link http://www.php.net/manual/en/closure.bind.php
     * @param Closure $closure The anonymous functions to bind.
     * @param object $newthis The object to which the given anonymous function should be bound, or NULL for the closure to be unbound.
     * @param mixed $newscope The class scope to which associate the closure is to be associated, or &#39;static&#39; to keep the current one.
     * If an object is given, the type of the object will be used instead.
     * This determines the visibility of protected and private methods of the bound object.
     * @return Closure Returns the newly created Closure object or FALSE on failure
     */
    static function bind(Closure $closure, $newthis, $newscope = &#39;static&#39;) { }
    /**
     * Temporarily binds the closure to newthis, and calls it with any given parameters.
     * @link http://php.net/manual/en/closure.call.php
     * @param object $newThis The object to bind the closure to for the duration of the call.
     * @param mixed $parameters [optional] Zero or more parameters, which will be given as parameters to the closure.
     * @return mixed
     * @since 7.0
     */
    function call ($newThis, ...$parameters) {}
    
    /**
     * @param callable $callable
     * @return Closure
     * @since 7.1
     */
    public static function fromCallable (callable $callable) {}
}

$app->get('/test', function () {
    echo $this->request->getMethod();
});

<?php
class Pandas {
    public $num = 1;
}
$pandas = new Pandas();
$add = function () {
    echo ++$this->num . PHP_EOL;
};
$newAdd1 = $add->bindTo($pandas);
$newAdd1();
// 输出 2
$newAdd2 = Closure::bind($add, $pandas);
$newAdd2();
// 输出 3

Fatal error: Uncaught Error: Cannot access protected property Pandas::$num

<?php
class Pandas {
    protected $num = 1;
}
$pandas = new Pandas();
$add = function () {
    echo ++$this->num . PHP_EOL;
};
$newAdd1 = $add->bindTo($pandas, $pandas);
$newAdd1();
// 输出 2
$newAdd2 = Closure::bind($add, $pandas, &#39;Pandas&#39;);
$newAdd2();
// 输出 3

<?php
class Pandas {
    protected $num = 1;
}
$pandas = new Pandas();
$add = function ($num) {
    $this->num += $num;
    echo $this->num . PHP_EOL;
};
$add->call($pandas, 5);
// 输出 6

<?php
class Foo
{
    protected $num = 1;
    public static function hello(string $bar)
    {
        echo &#39;hello &#39; . $bar;
    }
}
$hello = Closure::fromCallable([&#39;Foo&#39;, &#39;hello&#39;]);
$hello(&#39;world&#39;);