php Laravel 中的闭包是什么？
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What is Closure in Laravel?
提问by vishal ribdiya
I saw one Laravel function in middlewere:
我在中间看到了一个 Laravel 函数：
public function handle($request, Closure $next, $guard = null)
{
if (Auth::guard($guard)->check())
{
return redirect('/home');
}
return $next($request);
}
What is Closureand what does it do?
Closure它是什么以及它有什么作用？
回答by Amando Vledder
A Closureis an anonymous function. Closures are often used as callback methods and can be used as a parameter in a function.
一个封闭是一个匿名函数。闭包通常用作回调方法，并且可以用作函数中的参数。
If you take the following example:
如果你看下面的例子：
function handle(Closure $closure) {
$closure();
}
handle(function(){
echo 'Hello!';
});
We start by adding a Closureparameter the handlefunction. This will type hint us that the handlefunction takes a Closure.
我们首先Closure给handle函数添加一个参数。这将提示我们该handle函数采用Closure.
We then call the handlefunction and pass a function as the first parameter.
然后我们调用该handle函数并传递一个函数作为第一个参数。
By using $closure();in the handlefunction we tell PHP to execute the given Closurewhich will then echo 'Hello!'
通过$closure();在handle函数中使用我们告诉 PHP 执行给定的Closure，然后echo 'Hello!'
It is also possible to pass parameters into a Closure. We can do so by changing the Closurecall in the handlefunction to pass on a parameter. In this example i'll just pass a string but this can be any variable.
也可以将参数传递到Closure. 我们可以通过更改函数Closure中的handle调用来传递参数来实现。在这个例子中，我将只传递一个字符串，但这可以是任何变量。
The handle function now looks like
句柄函数现在看起来像
function handle(Closure $closure) {
$closure('Hello World!');
}
We now also need to modify the Closureitself to take the parameter. We do so by simply adding a parameter to the function. And then we pass that variable to the echo.
我们现在还需要修改Closure自身以获取参数。我们通过简单地向函数添加一个参数来实现。然后我们将该变量传递给echo.
The function now looks like
该功能现在看起来像
handle(function($value){
echo $value;
});
Which will echo Hello World!
哪个会回声 Hello World!
For more information you can check out these links:
有关更多信息，您可以查看以下链接：
http://php.net/manual/en/functions.anonymous.php
http://php.net/manual/en/functions.anonymous.php
