How to implement virtual method in php

Php virtual method implementation: First create a PHP sample file; then pass "

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Sharing of the implementation method of virtual functions in PHP5

Anyone who has studied C should know that there is a concept of virtual function in C. How to implement this virtual function in php5?

Please look at the following 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"; 
} 
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() covers A::x(), so 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( ) all call 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 running 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

The code is as follows:

<?php 
class ParentClass { 
static public function say( $str ) { 
static::do_print( $str ); 
} 
static public function do_print( $str ) { 
echo "<p>Parent says $str</p>"; 
} 
} 
class ChildClass extends ParentClass { 
static public function do_print( $str ) { 
echo "<p>Child says $str</p>"; 
} 
} 
class AnotherChildClass extends ParentClass { 
static public function do_print( $str ) { 
echo "<p>AnotherChild says $str</p>"; 
} 
} 
echo phpversion(); 
$a=new ChildClass(); 
$a->say( &#39;Hello&#39; ); 
$b=new AnotherChildClass(); 
$b->say( &#39;Hello&#39; );

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