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80 lines
11 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>Callback / Callable 类型</title>
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</head>
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<div id="layout">
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<div id="layout-content"><div id="language.types.callable" class="sect1">
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<h2 class="title">Callback / Callable 类型</h2>
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<p class="para">
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自 PHP 5.4 起可用 <span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> 类型指定回调类型
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callback。本文档基于同样理由使用 <span class="type"><a href="language.pseudo-types.html#language.types.callback" class="type callback">callback</a></span> 类型信息。
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</p>
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<p class="para">
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一些函数如 <span class="function"><a href="call_user_func.html" class="function">call_user_func()</a></span> 或
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<span class="function"><a href="usort.html" class="function">usort()</a></span> 可以接受用户自定义的回调函数作为参数。回调函数不止可以是简单函数，还可以是对象的方法，包括静态类方法。
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</p>
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<div class="sect2" id="language.types.callable.passing">
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<h3 class="title">传递</h3>
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<p class="para">
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PHP是将函数以<span class="type"><a href="language.types.string.html" class="type string">string</a></span>形式传递的。
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可以使用任何内置或用户自定义函数，但除了语言结构例如：<span class="function"><a href="array.html" class="function">array()</a></span>，<span class="function"><a href="echo.html" class="function">echo</a></span>，<span class="function"><a href="empty.html" class="function">empty()</a></span>，<span class="function"><a href="eval.html" class="function">eval()</a></span>，<span class="function"><a href="exit.html" class="function">exit()</a></span>，<span class="function"><a href="isset.html" class="function">isset()</a></span>，<span class="function"><a href="list.html" class="function">list()</a></span>，<span class="function"><a href="print.html" class="function">print</a></span>
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或 <span class="function"><a href="unset.html" class="function">unset()</a></span>。
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</p>
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<p class="para">
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一个已实例化的 <span class="type"><a href="language.types.object.html" class="type object">object</a></span> 的方法被作为 <span class="type"><a href="language.types.array.html" class="type array">array</a></span> 传递，下标 0 包含该 <span class="type"><a href="language.types.object.html" class="type object">object</a></span>，下标 1 包含方法名。
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在同一个类里可以访问 protected 和 private 方法。
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</p>
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<p class="para">
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静态类方法也可不经实例化该类的对象而传递，只要在下标 0 中包含类名而不是对象。自
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PHP 5.2.3 起，也可以传递 <em>'ClassName::methodName'</em>。
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</p>
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<p class="para">
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除了普通的用户自定义函数外，也可传递
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<a href="functions.anonymous.html" class="link">匿名函数</a> 给回调参数。
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</p>
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<p class="para">
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<div class="example" id="example-85">
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<p><strong>Example #1 回调函数示例</strong></p>
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<div class="example-contents">
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<div class="phpcode"><code><span style="color: #000000">
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<span style="color: #0000BB"><?php <br /><br /></span><span style="color: #FF8000">// An example callback function<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">my_callback_function</span><span style="color: #007700">() {<br /> echo </span><span style="color: #DD0000">'hello world!'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">// An example callback method<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">MyClass </span><span style="color: #007700">{<br /> static function </span><span style="color: #0000BB">myCallbackMethod</span><span style="color: #007700">() {<br /> echo </span><span style="color: #DD0000">'Hello World!'</span><span style="color: #007700">;<br /> }<br />}<br /><br /></span><span style="color: #FF8000">// Type 1: Simple callback<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(</span><span style="color: #DD0000">'my_callback_function'</span><span style="color: #007700">); <br /><br /></span><span style="color: #FF8000">// Type 2: Static class method call<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'MyClass'</span><span style="color: #007700">, </span><span style="color: #DD0000">'myCallbackMethod'</span><span style="color: #007700">)); <br /><br /></span><span style="color: #FF8000">// Type 3: Object method call<br /></span><span style="color: #0000BB">$obj </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(array(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">, </span><span style="color: #DD0000">'myCallbackMethod'</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">// Type 4: Static class method call (As of PHP 5.2.3)<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(</span><span style="color: #DD0000">'MyClass::myCallbackMethod'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Type 5: Relative static class method call (As of PHP 5.3.0)<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">A </span><span style="color: #007700">{<br /> public static function </span><span style="color: #0000BB">who</span><span style="color: #007700">() {<br /> echo </span><span style="color: #DD0000">"A\n"</span><span style="color: #007700">;<br /> }<br />}<br /><br />class </span><span style="color: #0000BB">B </span><span style="color: #007700">extends </span><span style="color: #0000BB">A </span><span style="color: #007700">{<br /> public static function </span><span style="color: #0000BB">who</span><span style="color: #007700">() {<br /> echo </span><span style="color: #DD0000">"B\n"</span><span style="color: #007700">;<br /> }<br />}<br /><br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'B'</span><span style="color: #007700">, </span><span style="color: #DD0000">'parent::who'</span><span style="color: #007700">)); </span><span style="color: #FF8000">// A<br /><br />// Type 6: Objects implementing __invoke can be used as callables (since PHP 5.3)<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">C </span><span style="color: #007700">{<br /> public function </span><span style="color: #0000BB">__invoke</span><span style="color: #007700">(</span><span style="color: #0000BB">$name</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">'Hello '</span><span style="color: #007700">, </span><span style="color: #0000BB">$name</span><span style="color: #007700">, </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /> }<br />}<br /><br /></span><span style="color: #0000BB">$c </span><span style="color: #007700">= new </span><span style="color: #0000BB">C</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(</span><span style="color: #0000BB">$c</span><span style="color: #007700">, </span><span style="color: #DD0000">'PHP!'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
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</span>
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</code></div>
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</div>
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</div>
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</p>
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<p class="para">
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<div class="example" id="example-86">
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<p><strong>Example #2 使用 Closure 的示例</strong></p>
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<div class="example-contents">
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<div class="phpcode"><code><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Our closure<br /></span><span style="color: #0000BB">$double </span><span style="color: #007700">= function(</span><span style="color: #0000BB">$a</span><span style="color: #007700">) {<br /> return </span><span style="color: #0000BB">$a </span><span style="color: #007700">* </span><span style="color: #0000BB">2</span><span style="color: #007700">;<br />};<br /><br /></span><span style="color: #FF8000">// This is our range of numbers<br /></span><span style="color: #0000BB">$numbers </span><span style="color: #007700">= </span><span style="color: #0000BB">range</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">5</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Use the closure as a callback here to <br />// double the size of each element in our <br />// range<br /></span><span style="color: #0000BB">$new_numbers </span><span style="color: #007700">= </span><span style="color: #0000BB">array_map</span><span style="color: #007700">(</span><span style="color: #0000BB">$double</span><span style="color: #007700">, </span><span style="color: #0000BB">$numbers</span><span style="color: #007700">);<br /><br />print </span><span style="color: #0000BB">implode</span><span style="color: #007700">(</span><span style="color: #DD0000">' '</span><span style="color: #007700">, </span><span style="color: #0000BB">$new_numbers</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
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</span>
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</code></div>
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</div>
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<div class="example-contents"><p>以上例程会输出：</p></div>
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<div class="example-contents screen">
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<div class="cdata"><pre>
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2 4 6 8 10
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</pre></div>
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</div>
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</div>
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</p>
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<blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">在函数中注册有多个回调内容时(如使用
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<span class="function"><a href="call_user_func.html" class="function">call_user_func()</a></span> 与 <span class="function"><a href="call_user_func_array.html" class="function">call_user_func_array()</a></span>)，如在前一个回调中有未捕获的异常，其后的将不再被调用。</p></p></blockquote>
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</div>
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</div></div></div></body></html> |