php 多态实现案例

<?php
//多态案例
//老师会画多边行，传一个图形让ta画就行了
class Teacher{
function drawPolygon(Polygon $polygon){ //弱语言，限定参数类型，php5.3+
$polygon->draw(); 
} 
}
//多边形,可定义为抽象类
class Polygon{
function draw(){
echo "draw a polygon";
}
}
//长方形
class ChangFangXing extends Polygon{
function draw(){
echo "draw a changfangxing";
}
}
//正方形
class ZhangFangXing extends Polygon{
function draw(){
echo "draw a zhangfangxing";
}
}
$teacher = new Teacher();
//画一个长方形
$teacher->drawPolygon(new ChangFangXing());//draw a changfangxing
echo "</br>";
//画一个正方方形
$teacher->drawPolygon(new ZhangFangXing());//draw a zhangfangxing
?>