PHP类和对象函数实例详解

1. interface_exists、class_exists、method_exists和property_exists:

      顾名思义，从以上几个函数的命名便可以猜出几分他们的功能。我想这也是我随着对PHP的深入学习而越来越喜欢这门编程语言的原因了吧。下面先给出他们的原型声明和简短说明，更多的还是直接看例子代码吧。
bool interface_exists (string $interface_name [, bool $autoload = true ]) 判断接口是否存在，第二个参数表示在查找时是否执行__autoload。
bool class_exists (string $class_name [, bool $autoload = true ]) 判断类是否存在，第二个参数表示在查找时是否执行__autoload。
bool method_exists (mixed $object , string $method_name) 判断指定类或者对象中是否含有指定的成员函数。
bool property_exists (mixed $class , string $property) 判断指定类或者对象中是否含有指定的成员变量。

<span style="color: #000000;">php
</span><strong><span style="color: #008000;">//</span></strong><span style="color: #008000;"><strong>in another_test_class.php</strong></span>
<span style="color: #0000ff;">interface</span><span style="color: #000000;"> AnotherTestInterface {

}

</span><span style="color: #0000ff;">class</span><span style="color: #000000;"> AnotherTestClass {
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> printMe() {
        </span><span style="color: #0000ff;">print</span> "This is Test2::printSelf.\n"<span style="color: #000000;">;
    }
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> doSomething() {
        </span><span style="color: #0000ff;">print</span> "This is Test2::doSomething.\n"<span style="color: #000000;">;
    }
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span> doSomethingWithArgs(<span style="color: #800080;">$arg1</span>, <span style="color: #800080;">$arg2</span><span style="color: #000000;">) {
        </span><span style="color: #0000ff;">print</span> 'This is Test2::doSomethingWithArgs with ($arg1 = '.<span style="color: #800080;">$arg1</span>.' and $arg2 = '.<span style="color: #800080;">$arg2</span>.").\n"<span style="color: #000000;">;
    }
}

</span><span style="color: #000000;">php
</span><strong><span style="color: #008000;">//</span></strong><span style="color: #008000;"><strong>in class_exist_test.php,</strong> 下面测试代码中所需的类和接口位于another_test_class.php，
//由此可以发现规律，类和接口的名称是驼峰风格的，而文件名的单词间是下划线分隔的。
//这里给出了两种__autoload的方式，因为第一种更为常用和方便，因此我们这里将第二种方式注释掉了，他们之间的差别可以查看manual。</span>
<span style="color: #0000ff;">function</span> __autoload(<span style="color: #800080;">$classname</span><span style="color: #000000;">) {
    </span><span style="color: #800080;">$nomilizedClassname</span> = <span style="color: #008080;">strtolower</span>(<span style="color: #008080;">preg_replace</span>('/([A-Z]\w*)([A-Z]\w*)([A-Z]\w*)/','${1}_${2}_${3}',<span style="color: #800080;">$classname</span><span style="color: #000000;">));
    </span><span style="color: #0000ff;">require</span> <span style="color: #008080;">strtolower</span>(<span style="color: #800080;">$nomilizedClassname</span>).".php"<span style="color: #000000;">;
}
</span><span style="color: #008000;">//</span><span style="color: #008000;">spl_autoload_register(function($classname) {
//    $nomilizedClassname = strtolower(preg_replace('/([A-Z]\w*)([A-Z]\w*)([A-Z]\w*)/','${1}_${2}_${3}',$classname));
//    require strtolower($nomilizedClassname).".php";
//});</span>

<span style="color: #0000ff;">print</span> "The following case is tested before executing autoload.\n"<span style="color: #000000;">;
</span><span style="color: #0000ff;">if</span> (!<span style="color: #008080;">class_exists</span>('AnotherTestClass',<span style="color: #0000ff;">false</span><span style="color: #000000;">)) {
    </span><span style="color: #0000ff;">print</span> "This class doesn't exist if no autoload.\n"<span style="color: #000000;">;
}

</span><span style="color: #0000ff;">if</span> (!<span style="color: #008080;">interface_exists</span>('AnotherTestInterface',<span style="color: #0000ff;">false</span><span style="color: #000000;">)) {
    </span><span style="color: #0000ff;">print</span> "This interface doesn't exist if no autoload.\n"<span style="color: #000000;">;
}

</span><span style="color: #0000ff;">print</span> "\nThe following case is tested after executing autoload.\n"<span style="color: #000000;">;
</span><span style="color: #0000ff;">if</span> (<span style="color: #008080;">class_exists</span>('AnotherTestClass',<span style="color: #0000ff;">true</span><span style="color: #000000;">)) {
    </span><span style="color: #0000ff;">print</span> "This class exists if autoload is set to true.\n"<span style="color: #000000;">;
}

</span><span style="color: #0000ff;">if</span> (<span style="color: #008080;">interface_exists</span>('AnotherTestInterface',<span style="color: #0000ff;">true</span><span style="color: #000000;">)) {
    </span><span style="color: #0000ff;">print</span> "This interface exists if autoload is set to true.\n"<span style="color: #000000;">;
}</span> 

    运行结果如下： 

<span style="color: #000000;">bogon:TestPhp$ php class_exist_test.php 
The following </span><span style="color: #000000;">case</span><span style="color: #000000;"> is tested before executing autoload.
This class doesn</span><span style="color: #800000;">'</span><span style="color: #800000;">t exist if no autoload.</span>
This interface doesn<span style="color: #800000;">'</span><span style="color: #800000;">t exist if no autoload.</span>
<span style="color: #000000;">
The following </span><span style="color: #000000;">case</span><span style="color: #000000;"> is tested after executing autoload.
</span><span style="color: #000000;">This class exists if autoload is set to true.
This interface exists if autoload is set to true.</span>

2. get_declared_classes和get_declared_interfaces: 

    分别返回当前可以访问的所有类和接口，这不仅包括自定义类和接口，也包括了PHP内置类和接口。他们的函数声明非常简单，没有参数，只是返回数组。见如下代码：

<span style="color: #000000;">php
</span><span style="color: #0000ff;">interface</span><span style="color: #000000;"> AnotherTestInterface {

}

</span><span style="color: #0000ff;">class</span><span style="color: #000000;"> AnotherTestClass {
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> printMe() {
        </span><span style="color: #0000ff;">print</span> "This is Test2::printSelf.\n"<span style="color: #000000;">;
    }
}

</span><span style="color: #008080;">print_r</span>(<span style="color: #008080;">get_declared_interfaces</span><span style="color: #000000;">());
</span><span style="color: #008080;">print_r</span>(<span style="color: #008080;">get_declared_classes</span>());

    由于输出结果过长，而且这两个函数也比较简单，所以下面就不再给出输出结果了。

3. get_class_methods、get_class_vars和get_object_vars： 

    这三个函数有一个共同点，即只能获取作用域可见范围内的所有成员函数、成员变量或非静态成员变量。比如在类的内部调用，则所有成员函数或者变量都符合条件，而在类的外部，则只有共有的函数和变量可以返回。
array get_class_methods (mixed $class_name) 获取指定类中可访问的成员函数。
array get_class_vars (string $class_name) 获取指定类中可以访问的成员变量。
array get_object_vars (object $object) 获取可以访问的非静态成员变量。

<span style="color: #000000;">php
</span><span style="color: #0000ff;">function</span> output_array(<span style="color: #800080;">$functionName</span>, <span style="color: #800080;">$items</span><span style="color: #000000;">) {
    </span><span style="color: #0000ff;">print</span> "<span style="color: #800080;">$functionName</span>.....................\n"<span style="color: #000000;">;
    </span><span style="color: #0000ff;">foreach</span> (<span style="color: #800080;">$items</span> <span style="color: #0000ff;">as</span> <span style="color: #800080;">$key</span> => <span style="color: #800080;">$value</span><span style="color: #000000;">) {
        </span><span style="color: #0000ff;">print</span> '$key = '.<span style="color: #800080;">$key</span>. ' => $value = '.<span style="color: #800080;">$value</span>."\n"<span style="color: #000000;">;
    }
}

</span><span style="color: #0000ff;">class</span><span style="color: #000000;"> TestClass {
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$publicVar</span> = 1<span style="color: #000000;">;
    </span><span style="color: #0000ff;">private</span> <span style="color: #800080;">$privateVar</span> = 2<span style="color: #000000;">;
    </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">private</span> <span style="color: #800080;">$staticPrivateVar</span> = "hello"<span style="color: #000000;">;
    </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">public</span> <span style="color: #800080;">$staticPublicVar</span><span style="color: #000000;">;

    </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> privateFunction() {

    }
    </span><span style="color: #0000ff;">function</span><span style="color: #000000;"> publicFunction() {
        output_array(</span>"get_class_methods",<span style="color: #008080;">get_class_methods</span>(<span style="color: #ff00ff;">__CLASS__</span><span style="color: #000000;">));
        output_array(</span>'get_class_vars',<span style="color: #008080;">get_class_vars</span>(<span style="color: #ff00ff;">__CLASS__</span><span style="color: #000000;">));
        output_array(</span>'get_object_vars',<span style="color: #008080;">get_object_vars</span>(<span style="color: #800080;">$this</span><span style="color: #000000;">));
    }
}

</span><span style="color: #800080;">$testObj</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> TestClass();
</span><span style="color: #0000ff;">print</span> "The following is output within TestClass.\n"<span style="color: #000000;">;
</span><span style="color: #800080;">$testObj</span>-><span style="color: #000000;">publicFunction();

</span><span style="color: #0000ff;">print</span> "\nThe following is output out of TestClass.\n"<span style="color: #000000;">;
output_array(</span>'get_class_methods',<span style="color: #008080;">get_class_methods</span>('TestClass'<span style="color: #000000;">));
output_array(</span>'get_class_vars',<span style="color: #008080;">get_class_vars</span>('TestClass'<span style="color: #000000;">));
output_array(</span>'get_object_vars',<span style="color: #008080;">get_object_vars</span>(<span style="color: #800080;">$testObj</span>));

    运行结果如下：

<span style="color: #000000;">bogon:TestPhp liulei$ php class_exist_test.php 
The following is output within TestClass.
get_class_methods.....................
$key </span>= <span style="color: #800080;">0</span> => $value =<span style="color: #000000;"> privateFunction
$key </span>= <span style="color: #800080;">1</span> => $value =<span style="color: #000000;"> publicFunction
get_class_vars.....................
$key </span>= publicVar => $value = <span style="color: #800080;">1</span><span style="color: #000000;">
$key </span>= privateVar => $value = <span style="color: #800080;">2</span><span style="color: #000000;">
$key </span>= staticPrivateVar => $value =<span style="color: #000000;"> hello
$key </span>= staticPublicVar => $value =<span style="color: #000000;"> 
get_object_vars.....................
$key </span>= publicVar => $value = <span style="color: #800080;">1</span><span style="color: #000000;">
$key </span>= privateVar => $value = <span style="color: #800080;">2</span><span style="color: #000000;">

The following is output out of TestClass.
get_class_methods.....................
$key </span>= <span style="color: #800080;">0</span> => $value =<span style="color: #000000;"> publicFunction
get_class_vars.....................
$key </span>= publicVar => $value = <span style="color: #800080;">1</span><span style="color: #000000;">
$key </span>= staticPublicVar => $value =<span style="color: #000000;"> 
get_object_vars.....................
$key </span>= publicVar => $value = <span style="color: #800080;">1</span>

4. get_called_class和get_class:

string get_class ([ object $object = NULL ]) 获取参数对象的类名称。
string get_called_class (void) 静态方法调用时当前的类名称。

<span style="color: #000000;">php
</span><span style="color: #0000ff;">class</span><span style="color: #000000;"> Base {
    </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> test() {
        </span><span style="color: #008080;">var_dump</span><span style="color: #000000;">(get_called_class());
    }
}

</span><span style="color: #0000ff;">class</span> Derive <span style="color: #0000ff;">extends</span><span style="color: #000000;"> Base {
}

Base</span>::<span style="color: #000000;">test();
Derive</span>::<span style="color: #000000;">test();

</span><span style="color: #008080;">var_dump</span>(<span style="color: #008080;">get_class</span>(<span style="color: #0000ff;">new</span><span style="color: #000000;"> Base()));
</span><span style="color: #008080;">var_dump</span>(<span style="color: #008080;">get_class</span>(<span style="color: #0000ff;">new</span> Derive()));

    运行结果如下：

<span style="color: #000000;">bogon:TestPhp$ php another_test_class.php 
</span><span style="color: #0000ff;">string</span>(<span style="color: #800080;">4</span>) <span style="color: #800000;">"</span><span style="color: #800000;">Base</span><span style="color: #800000;">"</span>
<span style="color: #0000ff;">string</span>(<span style="color: #800080;">6</span>) <span style="color: #800000;">"</span><span style="color: #800000;">Derive</span><span style="color: #800000;">"</span>
<span style="color: #0000ff;">string</span>(<span style="color: #800080;">4</span>) <span style="color: #800000;">"</span><span style="color: #800000;">Base</span><span style="color: #800000;">"</span>
<span style="color: #0000ff;">string</span>(<span style="color: #800080;">6</span>) <span style="color: #800000;">"</span><span style="color: #800000;">Derive</span><span style="color: #800000;">"</span>

5. get_parent_class、is_a和is_subclass_of:

    这三个函数都是和类的继承相关，所以我把他们归到了一起。

string get_parent_class ([ mixed $object ]) 获取参数对象的父类，如果没有父类则返回false。
bool is_a (object $object, string $class_name) 判断第一个参数对象是否是$class_name类本身或是其父类的对象。
bool is_subclass_of (mixed $object, string $class_name) 判断第一个参数对象是否是$class_name的子类。

<span style="color: #000000;">php
</span><span style="color: #0000ff;">class</span><span style="color: #000000;"> Base {
    </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> test() {
        </span><span style="color: #008080;">var_dump</span><span style="color: #000000;">(get_called_class());
    }
}

</span><span style="color: #0000ff;">class</span> Derive <span style="color: #0000ff;">extends</span><span style="color: #000000;"> Base {
}

</span><span style="color: #008080;">var_dump</span>(<span style="color: #008080;">get_parent_class</span>(<span style="color: #0000ff;">new</span><span style="color: #000000;"> Derive()));
</span><span style="color: #008080;">var_dump</span>(<span style="color: #008080;">is_a</span>(<span style="color: #0000ff;">new</span> Derive(),'Derive'<span style="color: #000000;">));
</span><span style="color: #008080;">var_dump</span>(<span style="color: #008080;">is_a</span>(<span style="color: #0000ff;">new</span> Derive(),'Base'<span style="color: #000000;">));
</span><span style="color: #008080;">var_dump</span>(<span style="color: #008080;">is_a</span>(<span style="color: #0000ff;">new</span> Base(),'Derive'<span style="color: #000000;">));

</span><span style="color: #008080;">var_dump</span>(<span style="color: #008080;">is_subclass_of</span>(<span style="color: #0000ff;">new</span> Derive(),'Derive'<span style="color: #000000;">));
</span><span style="color: #008080;">var_dump</span>(<span style="color: #008080;">is_subclass_of</span>(<span style="color: #0000ff;">new</span> Derive(),'Base'));

    运行结果如下：

<span style="color: #000000;">bogon:TestPhp$ php another_test_class.php 
</span><span style="color: #000000;">string(4) "Base"
bool(true)
bool(true)
bool(false)
bool(false)
bool(true)</span>