Please look at the code below:
Copy code The code is as follows:
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() ;
?>
In this example, A::y() calls A::x(), and B::x() overrides A::x() , then when calling B::y(), should B::y() call A::x() or B::x()? In C++, if A::x() is not defined as a virtual function, then B::y() (that is, A::y()) will call A::x(), and if A::x () is defined as a virtual function using the virtual keyword, then B::y() will call B::x(). However, in PHP5, the functionality of virtual functions is implemented by the self and $this keywords. If A::y() in the parent class calls A::x() using self::x(), then in the subclass no matter whether A::x() is overridden or not, A::y( ) calls A::x(); and if A::y() in the parent class calls A::x() using $this->x(), then if A::y() in the subclass ::x() is overridden by B::x(), A::y() will call B::x().
The results of the above example are as follows:
A::x() was called. A::y() was called. --
B::x() was called. A: :z() was called.
virtual-function.php
Copy code The code is as follows:
class ParentClass {
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' );
http://www.bkjia.com/PHPjc/323108.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/323108.htmlTechArticlePlease see the code below: Copy the code The code is as follows: ?php class A { public function x() { echo " A::x() was called.n"; } public function y() { self::x(); echo "A::y() was called.n";...
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