php面向对象要点[转]

• __construct

classConstructTest {private$arg1;
    private$arg2;

    publicfunction__construct($arg1, $arg2) {$this->arg1 = $arg1;
        $this->arg2 = $arg2;
        print"__construct is called...\n";
    }
    publicfunctionprintAttributes() {print'$arg1 = '.$this->arg1.' $arg2 = '.$this->arg2."\n";
    }
}
$testObject = new ConstructTest("arg1","arg2"); 
$testObject->printAttributes();

运行结果如下：

Stephens-Air:Desktop$ php Test.php 
__construct is called...
$arg1 = arg1 $arg2 = arg2

• parent

用于在子类中直接调用父类中的方法

classBaseClass {protected$arg1;
    protected$arg2;

    function__construct($arg1, $arg2) {$this->arg1 = $arg1;
        $this->arg2 = $arg2;
        print"__construct is called...\n";
    }
    functiongetAttributes() {return'$arg1 = '.$this->arg1.' $arg2 = '.$this->arg2;
    }
}

classSubClassextendsBaseClass {protected$arg3;

    function__construct($baseArg1, $baseArg2, $subArg3) {parent::__construct($baseArg1, $baseArg2);
        $this->arg3 = $subArg3;
    }
    functiongetAttributes() {returnparent::getAttributes().' $arg3 = '.$this->arg3;
    }
}
$testObject = new SubClass("arg1","arg2","arg3"); 
print$testObject->getAttributes()."\n";

运行结果如下：

Stephens-Air:Desktop$ php Test.php 
__construct is called...
$arg1 = arg1 $arg2 = arg2 $arg3 = arg3

• self
  在类内调用该类静态成员和静态方法的前缀修饰，对于非静态成员变量和函数则使用this。

classStaticExample {staticpublic$arg1 = "Hello, This is static field.\n";
    staticpublicfunctionsayHello() {printself::$arg1;
    }
}

print StaticExample::$arg1;
StaticExample::sayHello();

• static
  这里介绍的static关键字主要用于PHP 5.3以上版本新增的延迟静态绑定功能。

abstractclassBase {publicstaticfunctiongetInstance() {//这里的new static()实例化的是调用该静态方法的当前类。returnnewstatic();
    }
    abstractpublicfunctionprintSelf();}

classSubAextendsBase {publicfunctionprintSelf() {print"This is SubA::printSelf.\n";
    }
}

classSubBextendsBase {publicfunctionprintSelf() {print"This is SubB::printSelf.\n";
    }
}

SubA::getInstance()->printSelf();
SubB::getInstance()->printSelf();

运行结果如下：

Stephens-Air:Desktop$ php Test.php 
This is SubA::printSelf.
This is SubB::printSelf.

static关键字不仅仅可以用于实例化。和self和parent一样，static还可以作为静态方法调用的标识符，甚至是从非静态上下文中调用。在该场景下，self仍然表示的是当前方法所在的类。见如下代码：

abstractclassBase {private$ownedGroup;
    publicfunction__construct() {//这里的static和上面的例子一样，表示当前调用该方法的实际类。//需要另外说明的是，这里的getGroup方法即便不是静态方法，也会得到相同的结果。然而倘若//getGroup真的只是普通类方法，那么这里还是建议使用$this。$this->ownedGroup = static::getGroup();
    }
    publicfunctionprintGroup() {print"My Group is ".$this->ownedGroup."\n";
    }
    publicstaticfunctiongetInstance() {returnnewstatic();
    }
    publicstaticfunctiongetGroup() {return"default";
    }
}

classSubAextendsBase {
}

classSubBextendsBase {publicstaticfunctiongetGroup() {return"SubB";
    }
}

SubA::getInstance()->printGroup();
SubB::getInstance()->printGroup(); 

运行结果如下：

Stephens-Air:Desktop$ php Test.php 
My Groupisdefault
My Groupis SubB

• __destruct
  析构方法的作用和构造方法__construct刚好相反，它只是在对象被垃圾收集器收集之前自动调用，我们可以利用该方法做一些必要的清理工作。

classTestClass {function__destruct() {print"TestClass destructor is called.\n";
    }
}

$testObj = new TestClass();
unset($testObj);
print"Application will exit.\n";

运行结果如下：

Stephens-Air:Desktop$ php Test.php 
TestClass destructoriscalled.
Applicationwillexit.

• __clone
  在PHP 5之后的版本中，对象之间的赋值为引用赋值，即赋值后的两个对象将指向同一地址空间，如果想基于对象赋值，可以使用PHP提供的clone方法。该方法将当前对象浅拷贝之后的副本返回，如果想在clone的过程中完成一些特殊的操作，如深拷贝，则需要在当前类的声明中实现__clone方法，该方法在执行clone的过程中会被隐式调用。另外需要格外注意的是，__clone方法是作用再被拷贝的对象上，即赋值后的对象上执行。

classInnerClass {public$id = 10;
    publicfunctionprintSelf() {print'$id = '.$this->id."\n";
    }
}

classOuterClass {public$innerClass;
    publicfunction__construct() {$this->innerClass = new InnerClass();
    }
    publicfunction__clone() {$this->innerClass = clone$this->innerClass;
        print"__clone is called.\n";
    }
}

$outerA = new OuterClass();
print"Before calling to clone.\n";
$outerB = clone$outerA;
print"After calling to clone.\n";
$outerA->innerClass->id = 20;
print"In outerA: ";
$outerA->innerClass->printSelf();
print"In outerB: ";
$outerB->innerClass->printSelf();

运行结果如下：

Stephens-Air:Desktop$ php Test.php 
Before calling to clone.
__clone is called.
After calling to clone.In outerA: $id=20In outerB: $id=10

• const
  PHP5可以在类中定义常量属性。和全局常量一样，一旦定义就不能改变。常量属性不需要像普通属性那样以开头，按照惯例，只能用大写字母来命名常量。另外和静态属性一样，只能通过类而不能通过类的实例访问常量属性，引用常量时同样也不需要以

  以上就介绍了php面向对象要点[转]，包括了方面的内容，希望对PHP教程有兴趣的朋友有所帮助。