php interface_exists、class_exists、method_exists和property_exists介绍

下面我们一起来看在php 中PHP类和对象函数这 php interface_exists、class_exists、method_exists和property_exists详解,希望文章对各位同学会有所帮助。

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 [, boolautoload = 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 [, boolautoload = 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 , stringmethod_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 , stringproperty) //判断指定类或者对象中是否含有指定的成员变量。
<?php
//in another_test_class.php
interface AnotherTestInterface {

}

class AnotherTestClass {
    public static function printMe() {
        print "This is Test2::printSelf.n";
    }
    public function doSomething() {
        print "This is Test2::doSomething.n";
    }
    public function doSomethingWithArgs(arg1,arg2) {
        print 'This is Test2::doSomethingWithArgs with (arg1 = '.arg1.' and arg2 = '.arg2.").n";
    }
}

<?php
//in class_exist_test.php, 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。
function __autoload(classname) {nomilizedClassname = strtolower(preg_replace('/([A-Z]w*)([A-Z]w*)([A-Z]w*)/','{1}_{2}_{3}',classname));
    require strtolower(nomilizedClassname).".php";
}
//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";
//});

print "The following case is tested before executing autoload.n";
if (!class_exists('AnotherTestClass',false)) {
    print "This class doesn't exist if no autoload.n";
}

if (!interface_exists('AnotherTestInterface',false)) {
    print "This interface doesn't exist if no autoload.n";
}

print "nThe following case is tested after executing autoload.n";
if (class_exists('AnotherTestClass',true)) {
    print "This class exists if autoload is set to true.n";
}

if (interface_exists('AnotherTestInterface',true)) {
    print "This interface exists if autoload is set to true.n";
}

 运行结果如下:

bogon:TestPhp$ php class_exist_test.php
The following case is tested before executing autoload.
This class doesn't exist if no autoload.
This interface doesn't exist if no autoload.

The following case is tested after executing autoload.
This class exists if autoload is set to true.
This interface exists if autoload is set to true.

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:

<?php
interface AnotherTestInterface {

}

class AnotherTestClass {
    public static function printMe() {
        print "This is Test2::printSelf.n";
    }
}

print_r(get_declared_interfaces());
print_r(get_declared_classes());

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。

代码如下:


<?php
function output_array(functionName,items) {
    print "functionName.....................n";
    foreach (items as key =>value) {
        print 'key = '.key. ' => value = '.value."n";
    }
}

class TestClass {
    public publicVar = 1;
    privateprivateVar = 2;
    static private staticPrivateVar = "hello";
    static publicstaticPublicVar;

    private function privateFunction() {

    }
    function publicFunction() {
        output_array("get_class_methods",get_class_methods(__CLASS__));
        output_array('get_class_vars',get_class_vars(__CLASS__));
        output_array('get_object_vars',get_object_vars(this));
    }
}testObj = new TestClass();
print "The following is output within TestClass.n";
testObj->publicFunction();

print "nThe following is output out of TestClass.n";
output_array('get_class_methods',get_class_methods('TestClass'));
output_array('get_class_vars',get_class_vars('TestClass'));
output_array('get_object_vars',get_object_vars(testObj)); 

运行结果如下:

bogon:TestPhp liuleiphp class_exist_test.php
The following is output within TestClass.
get_class_methods.....................key = 0 => value = privateFunctionkey = 1 => value = publicFunction
get_class_vars.....................key = publicVar => value = 1key = privateVar => value = 2key = staticPrivateVar => value = hellokey = staticPublicVar => value =
get_object_vars.....................key = publicVar => value = 1key = privateVar => value = 2

The following is output out of TestClass.
get_class_methods.....................key = 0 => value = publicFunction
get_class_vars.....................key = publicVar => value = 1key = staticPublicVar => value =
get_object_vars.....................key = publicVar => value = 14. get_called_class和get_class:

string get_class ([ objectobject = 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。

<?php
class Base {
    static public function test() {
        var_dump(get_called_class());
    }
}

class Derive extends Base {
}

Base::test();
Derive::test();

var_dump(get_class(new Base()));
var_dump(get_class(new Derive()));   

运行结果如下:

bogon:TestPhp$ php another_test_class.php
string(4) "Base"
string(6) "Derive"
string(4) "Base"
string(6) "Derive"

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 (objectobject, 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, stringclass_name) 判断第一个参数对象是否是$class_name的子类。

代码如下:

<?php
class Base {
    static public function test() {
        var_dump(get_called_class());
    }
}

class Derive extends Base {
}

var_dump(get_parent_class(new Derive()));
var_dump(is_a(new Derive(),'Derive'));
var_dump(is_a(new Derive(),'Base'));
var_dump(is_a(new Base(),'Derive'));

var_dump(is_subclass_of(new Derive(),'Derive'));
var_dump(is_subclass_of(new Derive(),'Base')); 

运行结果如下:

bogon:TestPhp$ php another_test_class.php
string(4) "Base"
bool(true)
bool(true)
bool(false)
bool(false)
bool(true)

以上内容均为转载。

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