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数组运算符
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流程控制
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流程控制的替代语法
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declare
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include_once
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函数的参数
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返回值
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可变函数
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匿名函数
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类与对象
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属性
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类常量
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类的自动加载
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构造函数和析构函数
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对象继承
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范围解析操作符
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Static 关键字
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抽象类
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对象接口
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Trait
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匿名类
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重载
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遍历对象
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魔术方法
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Final 关键字
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对象复制
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对象比较
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类型约束
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后期静态绑定
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对象和引用
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对象序列化
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命名空间
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基本语法
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定义子命名空间
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在同一个文件中定义多个命名空间
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使用命名空间 - 基础
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命名空间和动态语言特征
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namespace 关键字和 __NAMESPACE__ 魔术常量
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使用命名空间 - 别名和导入
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<a href="../../.." >魔术方法</a>
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<h1 id="魔术方法">魔术方法</h1>
<p><code>__construct()</code> ， <code>__destruct()</code> ， <code>__call()</code> ， <code>__callStatic()</code> ， <code>__get()</code> ， <code>__set()</code> ， <code>__isset()</code> ， <code>__unset()</code> ， <code>__sleep()</code> ， <code>__wakeup()</code> ， <code>__toString()</code> ， <code>__invoke()</code> ， <code>__set_state()</code> ， <code>__clone()</code> 和 <code>__debugInfo()</code> 等方法在 PHP 中被称为魔术方法。</p>
<p>PHP 允许开发者在一个类中定义一个方法作为构造函数。具有构造函数的类会在每次创建新对象时先调用此方法，所以非常适合在使用对象之前做一些初始化工作。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Just a test property.
*
* @var string
*/</span>
<span class="token keyword">public</span> string <span class="token variable">$property</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Initialize the value of the property.
*
* @param void
* @return void
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__construct</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// string(3) "foo"</span>
</code></pre>
<p>PHP 引入了析构函数的概念，析构函数会在到某个对象的所有引用都被删除或者当对象被显式销毁时执行。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Just a test destructor.
*
* @param void
* @return void
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__destruct</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token single-quoted-string string">'foo'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">unset</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// string(3) "foo"</span>
</code></pre>
<p>在对象中调用一个不可访问方法时， <code>__call()</code> 会被调用。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Return the specified string.
*
* @param string $name
* @param array $args
* @return string
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__call</span><span class="token punctuation">(</span>string <span class="token variable">$name</span><span class="token punctuation">,</span> <span class="token keyword">array</span> <span class="token variable">$args</span><span class="token punctuation">)</span><span class="token punctuation">:</span> string
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token variable">$name</span> <span class="token punctuation">.</span> <span class="token single-quoted-string string">'+'</span> <span class="token punctuation">.</span> <span class="token function">implode</span><span class="token punctuation">(</span><span class="token single-quoted-string string">'+'</span><span class="token punctuation">,</span> <span class="token variable">$args</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token function">method</span><span class="token punctuation">(</span><span class="token single-quoted-string string">'foo'</span><span class="token punctuation">,</span> <span class="token single-quoted-string string">'bar'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// string(14) "method+foo+bar"</span>
</code></pre>
<p>在静态上下文中调用一个不可访问方法时， <code>__callStatic()</code> 会被调用。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Return the specified string.
*
* @param string $name
* @param array $args
* @return string
*/</span>
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">function</span> <span class="token function">__callStatic</span><span class="token punctuation">(</span>string <span class="token variable">$name</span><span class="token punctuation">,</span> <span class="token keyword">array</span> <span class="token variable">$args</span><span class="token punctuation">)</span><span class="token punctuation">:</span> string
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token variable">$name</span> <span class="token punctuation">.</span> <span class="token single-quoted-string string">'+'</span> <span class="token punctuation">.</span> <span class="token function">implode</span><span class="token punctuation">(</span><span class="token single-quoted-string string">'+'</span><span class="token punctuation">,</span> <span class="token variable">$args</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span>Foo<span class="token punctuation">:</span><span class="token punctuation">:</span><span class="token function">method</span><span class="token punctuation">(</span><span class="token single-quoted-string string">'foo'</span><span class="token punctuation">,</span> <span class="token single-quoted-string string">'bar'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// string(14) "method+foo+bar"</span>
</code></pre>
<p>在给不可访问属性赋值时， <code>__set()</code> 会被调用。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Set the value of the specified property.
*
* @param string $name
* @param string $value
* @return void
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__set</span><span class="token punctuation">(</span>string <span class="token variable">$name</span><span class="token punctuation">,</span> string <span class="token variable">$value</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token variable">$name</span> <span class="token operator">=</span> <span class="token variable">$value</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// string(3) "foo"</span>
</code></pre>
<p>读取不可访问属性的值时， <code>__get()</code> 会被调用。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Private property.
*
* @var string
*/</span>
<span class="token keyword">private</span> string <span class="token variable">$property</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Return the specified property.
*
* @param string $name
* @return string
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__get</span><span class="token punctuation">(</span>string <span class="token variable">$name</span><span class="token punctuation">)</span><span class="token punctuation">:</span> string
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token variable">$name</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// string(3) "foo"</span>
</code></pre>
<p>当对不可访问属性调用 <code>isset()</code> 或 <code>empty()</code> 时， <code>__isset()</code> 会被调用。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Private property.
*
* @var string
*/</span>
<span class="token keyword">private</span> string <span class="token variable">$property</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Check the specified property.
*
* @param string $name
* @return bool
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__isset</span><span class="token punctuation">(</span>string <span class="token variable">$name</span><span class="token punctuation">)</span><span class="token punctuation">:</span> bool
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token variable">$name</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// bool(true)</span>
</code></pre>
<p>当对不可访问属性调用 <code>unset()</code> 时， <code>__unset()</code> 会被调用。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Private property.
*
* @var string
*/</span>
<span class="token keyword">private</span> string <span class="token variable">$property</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Check the specified property.
*
* @param string $name
* @return bool
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__isset</span><span class="token punctuation">(</span>string <span class="token variable">$name</span><span class="token punctuation">)</span><span class="token punctuation">:</span> bool
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token variable">$name</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">/**
* Unset the specified property.
*
* @param string $name
* @return void
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__unset</span><span class="token punctuation">(</span>string <span class="token variable">$name</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token keyword">unset</span><span class="token punctuation">(</span><span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token variable">$name</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// bool(true)</span>
<span class="token keyword">unset</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// bool(false)</span>
</code></pre>
<p><code>serialize()</code> 函数会检查类中是否存在一个魔术方法 <code>__sleep()</code> 。如果存在，该方法会先被调用，然后才执行序列化操作。此功能可以用于清理对象，并返回一个包含对象中所有应被序列化的变量名称的数组。如果该方法未返回任何内容，则 <code>NULL</code> 被序列化，并产生一个 <code>E_NOTICE</code> 级别的错误。 <code>__sleep()</code> 方法常用于提交未提交的数据，或类似的清理操作。同时，如果有一些很大的对象，但不需要全部保存，这个功能就很好用。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Public property.
*
* @var string
*/</span>
<span class="token keyword">public</span> string <span class="token variable">$public</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'public'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Protected property.
*
* @var string
*/</span>
<span class="token keyword">protected</span> string <span class="token variable">$protected</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'protected'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Private property.
*
* @var string
*/</span>
<span class="token keyword">private</span> string <span class="token variable">$private</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'private'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Return an array of the specified properties.
*
* @param void
* @return array
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__sleep</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">:</span> <span class="token keyword">array</span>
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token punctuation">[</span><span class="token single-quoted-string string">'public'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token function">serialize</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// string(40) "O:3:"Foo":1:{s:6:"public";s:6:"public";}"</span>
</code></pre>
<p>与之相反， <code>unserialize()</code> 会检查是否存在一个 <code>__wakeup()</code> 方法。如果存在，则会先调用 <code>__wakeup()</code> 方法，预先准备对象需要的资源。 <code>__wakeup()</code> 经常用在反序列化操作中，例如重新建立数据库连接，或执行其它初始化操作。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Public property.
*
* @var string
*/</span>
<span class="token keyword">public</span> string <span class="token variable">$public</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'public'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Protected property.
*
* @var string
*/</span>
<span class="token keyword">protected</span> string <span class="token variable">$protected</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'protected'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Private property.
*
* @var string
*/</span>
<span class="token keyword">private</span> string <span class="token variable">$private</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'private'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Set the value of the specified property.
*
* @param void
* @return void
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__wakeup</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'O:3:"Foo":1:{s:6:"public";s:6:"public";}'</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token function">unserialize</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// object(Foo)#1 (4) { ["public"]=> string(6) "public" ["protected":protected]=> string(9) "protected" ["private":"Foo":private]=> string(7) "private" ["property"]=> string(3) "foo" }</span>
</code></pre>
<p><code>__toString()</code> 方法用于一个类被当成字符串时应怎样回应。此方法必须返回一个字符串，否则将发出一条 <code>E_RECOVERABLE_ERROR</code> 级别的致命错误。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Return a string.
*
* @param void
* @return string
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__toString</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">:</span> string
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token variable">$foo</span> <span class="token punctuation">.</span> <span class="token double-quoted-string string">"\r\n"</span><span class="token punctuation">;</span> <span class="token comment">// foo</span>
<span class="token keyword">print</span> <span class="token variable">$foo</span> <span class="token punctuation">.</span> <span class="token double-quoted-string string">"\r\n"</span><span class="token punctuation">;</span> <span class="token comment">// foo</span>
</code></pre>
<p>当尝试以调用函数的方式调用一个对象时， <code>__invoke()</code> 方法会被自动调用。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Return a string.
*
* @param void
* @return string
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__invoke</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">:</span> string
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// string(3) "foo"</span>
</code></pre>
<p>当调用 <code>var_export()</code> 函数导出类的相关信息时， <code>__set_state()</code> 静态方法会被调用。此方法的唯一参数是一个数组，其中包含按数组键值对格式排列的类属性。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Just a test property.
*
* @var string
*/</span>
<span class="token keyword">public</span> string <span class="token variable">$property</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Return an initialized object.
*
* @param array $array
* @return Foo
*/</span>
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">function</span> <span class="token function">__set_state</span><span class="token punctuation">(</span><span class="token keyword">array</span> <span class="token variable">$array</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Foo
<span class="token punctuation">{</span>
<span class="token variable">$object</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">self</span><span class="token punctuation">;</span>
<span class="token variable">$object</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span> <span class="token operator">=</span> <span class="token variable">$array</span><span class="token punctuation">[</span><span class="token single-quoted-string string">'property'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">return</span> <span class="token variable">$object</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$foo</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">property</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">;</span>
<span class="token function">var_export</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// Foo::__set_state(array( 'property' => 'foo', ))</span>
<span class="token variable">$bar</span> <span class="token operator">=</span> Foo<span class="token punctuation">:</span><span class="token punctuation">:</span><span class="token function">__set_state</span><span class="token punctuation">(</span><span class="token keyword">array</span><span class="token punctuation">(</span> <span class="token single-quoted-string string">'property'</span> <span class="token operator">=</span><span class="token operator">></span> <span class="token single-quoted-string string">'foo'</span><span class="token punctuation">,</span> <span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$bar</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// object(Foo)#2 (1) { ["property"]=> string(3) "foo" }</span>
</code></pre>
<p>对象复制可以通过 <code>clone</code> 关键字来完成（如果可能，这将调用对象的 <code>__clone()</code> 方法）。对象中的 <code>__clone()</code> 方法不能被直接调用。当对象被复制后， PHP 会对对象的所有属性执行一个浅复制。所有的引用属性仍然会是一个指向原来的变量的引用。当复制完成时，如果定义了 <code>__clone()</code> 方法，则新创建的对象（复制生成的对象）中的 <code>__clone()</code> 方法会被调用，可用于修改属性的值（如果有必要的话）。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Cat</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* The name of cat.
*
* @var string
*/</span>
<span class="token keyword">public</span> string <span class="token variable">$name</span><span class="token punctuation">;</span>
<span class="token comment">/**
* The age of cat.
*
* @var int
*/</span>
<span class="token keyword">public</span> int <span class="token variable">$age</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Store the name and age.
*
* @param string $name
* @param int $age
* @return void
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__construct</span><span class="token punctuation">(</span>string <span class="token variable">$name</span><span class="token punctuation">,</span> int <span class="token variable">$age</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">name</span> <span class="token operator">=</span> <span class="token variable">$name</span><span class="token punctuation">;</span>
<span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">age</span> <span class="token operator">=</span> <span class="token variable">$age</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token keyword">class</span> <span class="token class-name">Dog</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* The name of dog.
*
* @var string
*/</span>
<span class="token keyword">public</span> string <span class="token variable">$name</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Store an instance of cat.
*
* @var Cat
*/</span>
<span class="token keyword">public</span> Cat <span class="token variable">$cat</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Complete deep copy.
*
* @param void
* @return void
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__clone</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">cat</span> <span class="token operator">=</span> <span class="token keyword">clone</span> <span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">cat</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$spike</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Dog</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$spike</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">name</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'Spike'</span><span class="token punctuation">;</span>
<span class="token variable">$spike</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">cat</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Cat</span><span class="token punctuation">(</span><span class="token single-quoted-string string">'Tom'</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$tyke</span> <span class="token operator">=</span> <span class="token keyword">clone</span> <span class="token variable">$spike</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$spike</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// object(Dog)#1 (2) { ["name"]=> string(5) "Spike" ["cat"]=> object(Cat)#2 (2) { ["name"]=> string(3) "Tom" ["age"]=> int(6) } }</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$tyke</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// object(Dog)#3 (2) { ["name"]=> string(5) "Spike" ["cat"]=> object(Cat)#4 (2) { ["name"]=> string(3) "Tom" ["age"]=> int(6) } }</span>
<span class="token variable">$tyke</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">name</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'Tyke'</span><span class="token punctuation">;</span>
<span class="token variable">$tyke</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">cat</span><span class="token operator">-</span><span class="token operator">></span><span class="token property">age</span> <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$spike</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// object(Dog)#1 (2) { ["name"]=> string(5) "Spike" ["cat"]=> object(Cat)#2 (2) { ["name"]=> string(3) "Tom" ["age"]=> int(6) } }</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$tyke</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// object(Dog)#3 (2) { ["name"]=> string(4) "Tyke" ["cat"]=> object(Cat)#4 (2) { ["name"]=> string(3) "Tom" ["age"]=> int(2) } }</span>
</code></pre>
<p>当调用 <code>var_dump()</code> 函数打印类的相关信息时， <code>__debugInfo</code> 方法会被调用。如果未在对象上定义该方法，则将显示所有公共属性，受保护属性和私有属性。</p>
<pre class="language-"><code class="lang-php"><span class="token delimiter important"><?php</span>
<span class="token keyword">class</span> <span class="token class-name">Foo</span>
<span class="token punctuation">{</span>
<span class="token comment">/**
* Public property.
*
* @var string
*/</span>
<span class="token keyword">public</span> string <span class="token variable">$public</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'public'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Protected property.
*
* @var string
*/</span>
<span class="token keyword">protected</span> string <span class="token variable">$protected</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'protected'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Private property.
*
* @var string
*/</span>
<span class="token keyword">private</span> string <span class="token variable">$private</span> <span class="token operator">=</span> <span class="token single-quoted-string string">'private'</span><span class="token punctuation">;</span>
<span class="token comment">/**
* Return all visibility properties.
*
* @param void
* @return array
*/</span>
<span class="token keyword">public</span> <span class="token keyword">function</span> <span class="token function">__debugInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">:</span> <span class="token keyword">array</span>
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token punctuation">[</span>
<span class="token single-quoted-string string">'public'</span> <span class="token operator">=</span><span class="token operator">></span> <span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token keyword">public</span><span class="token punctuation">,</span>
<span class="token single-quoted-string string">'protected'</span> <span class="token operator">=</span><span class="token operator">></span> <span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token keyword">protected</span><span class="token punctuation">,</span>
<span class="token single-quoted-string string">'private'</span> <span class="token operator">=</span><span class="token operator">></span> <span class="token variable">$this</span><span class="token operator">-</span><span class="token operator">></span><span class="token keyword">private</span>
<span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token variable">$foo</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Foo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token variable">$foo</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// object(Foo)#1 (3) { ["public"]=> string(6) "public" ["protected"]=> string(9) "protected" ["private"]=> string(7) "private" }</span>
</code></pre>
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