blocks|key|254223|text|它们的工作方式大致相同。下面是关于PHP实现的更多信息：http://php.net/manual/en/functions.anonymous.php|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|254224|您可以使用闭包(在PHP中称为“匿名函数”)作为回调：|254225|//+return+array+of+ids
return+array_map(+function(+$a+)+{+return+$a['item_id'];+},+$items_arr+);|code-block|syntax|javascript|254226|并将其赋给一个变量：|254227|$greet+=+function(+$string+)+{+echo+'Hello+'+.+$string;+};+//+note+the+;+!
echo+$greet('Rijk');+//+"Hello+Rijk"|254228|此外，匿名函数“继承”定义它们的作用域-就像JS实现一样，有一个问题:您必须在use()中列出您想要继承的所有变量|style|BOLD|CODE|254229|function+normalFunction(+$parameter+)+{
++++$anonymous+=+function()+use(+$parameter+)+{+/*+...+*/+};
}|254230|如果您想要修改原始变量，则可以作为参考。|254231|function+normalFunction(+$parameter+)+{
++++$anonymous+=+function()+use(+&$parameter+)+{+$parameter+%2B%2B+};
++++$anonymous();
++++$parameter;+//+will+be+%2B+1
}|254232|entityMap|0|LINK|mutability|MUTABLE|url|http://php.net/manual/en/functions.anonymous.php^0|S|1C|0|0|0|0|0|0|T|S|13|5|0|0|0|K|0|0^^$0|@$1|2|3|4|5|6|7|17|8|@]|9|@$A|18|B|19|1|1A]]|C|$]]|$1|D|3|E|5|6|7|1B|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|1C|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|1D|8|@]|9|@]|C|$]]|$1|M|3|N|5|H|7|1E|8|@]|9|@]|C|$I|J]]|$1|O|3|P|5|6|7|1F|8|@$A|1G|B|1H|Q|R]|$A|1I|B|1J|Q|S]]|9|@]|C|$]]|$1|T|3|U|5|H|7|1K|8|@]|9|@]|C|$I|J]]|$1|V|3|W|5|6|7|1L|8|@$A|1M|B|1N|Q|R]]|9|@]|C|$]]|$1|X|3|Y|5|H|7|1O|8|@]|9|@]|C|$I|J]]|$1|Z|3|-4|5|6|7|1P|8|@]|9|@]|C|$]]]|10|$11|$5|12|13|14|C|$15|16]]]]

They do pretty much work the same way. Here's more information about the PHP implementation: <a href="http://php.net/manual/en/functions.anonymous.php" rel="nofollow">http://php.net/manual/en/functions.anonymous.php</a>

You can use a closure (in PHP called 'anonymous function') as a callback:

<pre><code>// return array of ids
return array_map( function( $a ) { return $a['item_id']; }, $items_arr );
</code></pre>

and assign it to a variable:

<pre><code>$greet = function( $string ) { echo 'Hello ' . $string; }; // note the ; !
echo $greet('Rijk'); // "Hello Rijk"
</code></pre>

Furthermore, anonymous function 'inherit' the scope in which they were defined - just as the JS implementation, with one gotcha: you have to list all variables you want to inherit in a <code>use()</code>:

<pre><code>function normalFunction( $parameter ) {
 $anonymous = function() use( $parameter ) { /* ... */ };
}
</code></pre>

and as a reference if you want to modify the orignal variable.

<pre><code>function normalFunction( $parameter ) {
 $anonymous = function() use( &amp;$parameter ) { $parameter ++ };
 $anonymous();
 $parameter; // will be + 1
}
</code></pre>

blocks|key|252583|text|一个不同之处在于两者如何处理匿名函数在其中执行的上下文的存储：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|252584|//+JavaScript:
var+a+=+1;
var+f+=+function()+{
+++console.log(a);
};
a+=+2;
f();
//+will+echo+2;

//+PHP
$a+=+1;
$f+=+function()+{
++++echo+$a;
};
$a+=+2;
$f();
//+will+result+in+a+"PHP+Notice:++Undefined+variable:+a+in+Untitled.php+on+line+5"|code-block|syntax|javascript|252585|要修复此通知，您必须使用use语法：|offset|length|style|CODE|252586|$a+=+1;
$f+=+function()+use+($a)+{
++++echo+$a;
};
$a+=+2;
$f();
//+but+this+will+echo+1+instead+of+2+(like+JavaScript)|252587|要让匿名函数在某种程度上类似于JavaScript对应函数，您必须使用引用：|252588|$a+=+1;
$f+=+function()+use+(&$a)+{
++++echo+$a;
};
$a+=+2;
$f();
//+will+echo+2|252589|我认为这是JavaScript和PHP闭包之间最显著的区别。|252590|的第二个不同之处在于，每个JavaScript闭包都有一个可用的this上下文，这意味着，您可以在闭包本身中使用this+(尽管弄清楚this实际指的是什么通常是相当复杂的)-PHP的当前稳定版本(PHP5.3)还不支持在闭包中使用$this，但PHP的即将到来的版本(PHP5.4)将支持使用$closure->bind($this)的$this绑定和重新绑定(有关更多信息，请参阅Object+Extension+RFC+)。|252591|第三个差异是两种语言处理分配给对象属性的闭包的方式：|BOLD|252592|//+JavaScript
var+a+=+{
++++b:+function()+{}
};
a.b();+//+works


//+PHP
$a+=+new+stdClass();
$a->b+=+function()+{};
$a->b();+//+does+not+work+"PHP+Fatal+error:++Call+to+undefined+method+stdClass::b()+in+Untitled.php+on+line+4"

$f+=+$a->b;
$f();+//+works+though|252593|如果闭包被分配给类定义中的属性，情况也是如此：|252594|class+A+{
++++public+$b;

++++public+function+__construct()+{
++++++++$this->b+=+function()+{};
++++}

++++public+function+c()+{
++++++++$this->b();
++++}
}
$a+=+new+A();
//+neither
$a->b();
//+nor
$a->c();
//+do+work|252595|第四个区别：+JavaScript闭包是完全成熟的对象，而在中它们是受限对象。例如，PHP闭包不能有自己的属性：|252596|$fn+=+function()+{};
$fn->foo+=+1;
//+->+Catchable+fatal+error:+Closure+object+cannot+have+properties|252597|在JavaScript中，您可以执行以下操作：|252598|var+fn+=+function()+{};
fn.foo+=+1;
fn.foo;+//+1|252599|Javascript第五个不同之处：返回的闭包可以在中立即调用：|252600|var+fn+=+function()+{+return+function()+{+alert('Hi');}}
fn()();++++|252601|不是在PHP中：|252602|$fn+=+function()+{+return+function()+{+echo('Hi');};};
$fn()();+++++//+syntax+error|252603|entityMap|0|LINK|mutability|MUTABLE|url|https://wiki.php.net/rfc/closures/object-extension?s%255B%255D=closure^0|0|0|C|3|0|0|0|0|0|W|4|1K|4|1V|4|38|5|43|L|4P|5|5C|K|0|0|0|5|0|0|0|0|U|Q|0|0|0|N|0|0|0|I|Q|6|0|0|0|8|0|0^^$0|@$1|2|3|4|5|6|7|1T|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1U|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1V|8|@$I|1W|J|1X|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|1Y|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|20|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|21|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|22|8|@$I|23|J|24|K|L]|$I|25|J|26|K|L]|$I|27|J|28|K|L]|$I|29|J|2A|K|L]|$I|2B|J|2C|K|L]|$I|2D|J|2E|K|L]]|9|@$I|2F|J|2G|1|2H]]|A|$]]|$1|W|3|X|5|6|7|2I|8|@$I|2J|J|2K|K|Y]]|9|@]|A|$]]|$1|Z|3|10|5|D|7|2L|8|@]|9|@]|A|$E|F]]|$1|11|3|12|5|6|7|2M|8|@]|9|@]|A|$]]|$1|13|3|14|5|D|7|2N|8|@]|9|@]|A|$E|F]]|$1|15|3|16|5|6|7|2O|8|@$I|2P|J|2Q|K|Y]]|9|@]|A|$]]|$1|17|3|18|5|D|7|2R|8|@]|9|@]|A|$E|F]]|$1|19|3|1A|5|6|7|2S|8|@$I|2T|J|2U|K|Y]]|9|@]|A|$]]|$1|1B|3|1C|5|D|7|2V|8|@]|9|@]|A|$E|F]]|$1|1D|3|1E|5|6|7|2W|8|@$I|2X|J|2Y|K|Y]|$I|2Z|J|30|K|Y]]|9|@]|A|$]]|$1|1F|3|1G|5|D|7|31|8|@]|9|@]|A|$E|F]]|$1|1H|3|1I|5|6|7|32|8|@$I|33|J|34|K|Y]]|9|@]|A|$]]|$1|1J|3|1K|5|D|7|35|8|@]|9|@]|A|$E|F]]|$1|1L|3|-4|5|6|7|36|8|@]|9|@]|A|$]]]|1M|$1N|$5|1O|1P|1Q|A|$1R|1S]]]]

One difference is how both cope with storing the context in which an anonymous function is executed:

<pre><code>// JavaScript:
var a = 1;
var f = function() {
 console.log(a);
};
a = 2;
f();
// will echo 2;

// PHP
$a = 1;
$f = function() {
 echo $a;
};
$a = 2;
$f();
// will result in a "PHP Notice: Undefined variable: a in Untitled.php on line 5"
</code></pre>

To fix this notice you'll have to use the <code>use</code> syntax:

<pre><code>$a = 1;
$f = function() use ($a) {
 echo $a;
};
$a = 2;
$f();
// but this will echo 1 instead of 2 (like JavaScript)
</code></pre>

To have the anonymous function behave somehow like the JavaScript counterpart you'll have to use references:

<pre><code>$a = 1;
$f = function() use (&amp;$a) {
 echo $a;
};
$a = 2;
$f();
// will echo 2
</code></pre>

I think this is the most striking difference between JavaScript and PHP closures.

Second difference is that every JavaScript closure has a <code>this</code> context available which means, that you can use <code>this</code> inside the closure itself (although it's often quite complicated to figure out what <code>this</code> actually refers to) - PHP's current stable version (PHP 5.3) does not yet support <code>$this</code> inside a closure, but PHP's upcoming version (PHP 5.4) will support <code>$this</code> binding and rebinding using <code>$closure-&gt;bind($this)</code> (See the <a href="https://wiki.php.net/rfc/closures/object-extension?s%5B%5D=closure" rel="noreferrer">Object Extension RFC</a> for more info.)

Third difference is how both languages treat closures assigned to object properties:

<pre><code>// JavaScript
var a = {
 b: function() {}
};
a.b(); // works


// PHP
$a = new stdClass();
$a-&gt;b = function() {};
$a-&gt;b(); // does not work "PHP Fatal error: Call to undefined method stdClass::b() in Untitled.php on line 4"

$f = $a-&gt;b;
$f(); // works though
</code></pre>

The same is true if closures are assigned to properties in class definitions:

<pre><code>class A {
 public $b;

 public function __construct() {
 $this-&gt;b = function() {};
 }

 public function c() {
 $this-&gt;b();
 }
}
$a = new A();
// neither
$a-&gt;b();
// nor
$a-&gt;c();
// do work
</code></pre>

Fourth difference: JavaScript Closures are full fledged objects, wheres in PHP they are restricted objects. For instance, PHP Closures cannot have properties of their own:

<pre><code>$fn = function() {};
$fn-&gt;foo = 1;
// -&gt; Catchable fatal error: Closure object cannot have properties
</code></pre>

while in JavaScript you can do:

<pre><code>var fn = function() {};
fn.foo = 1;
fn.foo; // 1
</code></pre>

Fifth difference: Returned closures can be immediately called upon in Javascript:

<pre><code>var fn = function() { return function() { alert('Hi');}}
fn()(); 
</code></pre>

Not in PHP:

<pre><code>$fn = function() { return function() { echo('Hi');};};
$fn()(); // syntax error
</code></pre>

blocks|key|3152789|text|我在PHP中发现的唯一一件事(它非常酷，而且非常方便！)是在类中使用它们作为getters和setters的能力，这在以前一直是一个噩梦，JavaScript可以以相同的方式使用，但它们的行为与我看到的几乎相同。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3152790|我不确定两者之间的命名空间约定差异，但正如@Rijk指出的那样，PHP网站上有一个专门介绍它们的部分|3152791|<?php+
++++class+testing+{
++++++++private+$foo+=+'Hello+';
++++++++public+$bar++=+'Bar';

++++++++#Act+like+a+getter+and+setter!
++++++++public+static+$readout+=+function+($val+=+null)+{
++++++++++++if+(!empty($val))+{
++++++++++++++++testing::$readout+=+$val;
++++++++++++}
++++++++++++return+testing::$readout;
++++++++}
++++}|code-block|syntax|javascript|3152792|它们对……来说也很棒。|offset|length|style|BOLD|3152793|使用控制器循环访问项，而不是页面上的新for/each循环|3152794|非常适合作为参数提供给函数/类|3152795|让人讨厌的是……|3152796|你不能对它们进行类型转换，因为它们只是函数...|3152797|entityMap^0|0|0|0|0|5|0|0|0|0|8|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|11|8|@$K|12|L|13|M|N]]|9|@]|A|$]]|$1|O|3|P|5|6|7|14|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|16|8|@$K|17|L|18|M|N]]|9|@]|A|$]]|$1|U|3|V|5|6|7|19|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|X|$]]

The only thing I've found in PHP (that is totally cool and really handy!) is the ability to use them as getters and setters in classes which was always a nightmare to achieve before, JavaScript can be used in the same way but they do both act almost identically from what I've seen.

I'm not sure about the namespacing convention differences between the two but as @Rijk pointed out there is a section on the PHP website dedicated to them

<pre><code>&lt;?php 
 class testing {
 private $foo = 'Hello ';
 public $bar = 'Bar';

 #Act like a getter and setter!
 public static $readout = function ($val = null) {
 if (!empty($val)) {
 testing::$readout = $val;
 }
 return testing::$readout;
 }
 }
</code></pre>

They are also really great for...

Looping through items with a controller rather than a new for/each loop on the page

Great for supplying as arguments to functions/classes

Whats annoying about them is...

You can't typecast them, since they're just functions...

What are the differences between closures in JS and closures in PHP? Do they pretty much work the same way? Are there any caveats to be aware of when writing closures in PHP?

Javascript closures vs PHP closures, what's the difference?

JS中的闭包和PHP中的闭包有什么不同？它们的工作方式大致相同吗？在用PHP编写闭包时有什么需要注意的地方吗？

问Javascript闭包与PHP闭包有什么不同？
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