h5 PHP5中虛函數的實作方法分享

請看下面的程式碼：

複製程式碼 程式碼如下:

class A {
public function x() {
echo "A::x() was called.n";
}
public function y() {
self::x();
echo "A::y() was called.n";
}
public function z(​​) {
$this->x();
echo "A::z() was called .n";
}
}
class B extends A {
public function x() {
echo "B::x() was called.n";
}
}
$b = new B();
$b->y();
echo "--n";
$b->z();
?>

該例中，A::y()調用了A::x()，而B::x()覆蓋了A::x()，那麼當呼叫B ::y()時，B::y()應該呼叫A::x()還是B::x()呢？在C++中，如果A::x()未被定義為虛擬函數，那麼B::y()（也就是A::y()）將會呼叫A::x()，而如果A::x ()使用virtual關鍵字定義成虛擬函數，那麼B::y()將會呼叫B::x()。然而，在PHP5中，虛函數的功能是由 self 和 $this 關鍵字實現的。如果父類別中A::y()中使用self::x() 的方式呼叫了A::x()，那麼在子類別中不論A::x()是否被覆蓋，A::y( )呼叫的都是A::x()；而如果父類別中A::y()使用$this->x() 的方式呼叫了A::x()，那麼如果在子類別中A: :x()被B::x()覆蓋，A::y()將會呼叫B::x()。
上例的運作結果如下：
A::x() was called. A::y() was called. --
B::x() was called. A::z( ) was called.
virtual-function.php

複製程式碼 程式碼如下:

static public function say( $str ) {
static::do_print( $str );
}
static public function do_print( $str ) {
echo "

Parent says $str

";
}
}
class ChildClass extends ParentClass {
static public function do_print( $str ) {
echo "

Child says $ str

";
}
}
class AnotherChildClass extends ParentClass {
static public function do_print( $str ) {
echo "

AnotherChild says $str

";
}
}
echo phpversion();
$a=new ChildClass();
$a->say( 'Hello' );
$b= new AnotherChildClass();
$b->say( 'Hello' );


以上就介紹了h5 PHP5中虛函數的實作方法分享，包含了h5方面的內容，希望對PHP教學有興趣的朋友有幫助。