该页面无法处理请求。在本地主机上运行 php

Question

我在本地主机上运行这段代码。在http://localhost:8000/Polymorphism.php上运行时出现错误。这是php上的一个简单的多态代码。其他代码运行起来很轻松，但是运行这段代码就出错了。此页面不工作本地主机当前无法处理此请求。HTTP 错误 500<?phppublic interface Shape{   public function calculateArea();}  public class Circle implements Shape{  private $radius;  public function __construct($r){   $this->radius=$r;  }  public function calculateArea(){  echo 'Area of circle = '.pi()* $this->radius*$this->radius.'<br>';  }}class Rectangle implements Shape{ private $height; private $width; public function __construct($h,$w){  this->height=$h;  this->width=$w; } public function calculateArea(){ echo 'Area of a Rectangle=' .$this->height.$this->width.'<br>'; } } $circle= new Circle(5); $rect= new Rectangle(10,20); $circle->calculateArea(); $rect->calculateArea();?>

Answer 1

您永远不会为类或接口分配访问修饰符。它们仅用于指定方法和属性。你在课堂上还有两个错误，Rectangle你应该提到高度和宽度

  $this->height=$h;

  $this->width=$w;

将您的整体代码更改为

<?php

interface Shape{

 public function calculateArea();

} 

class Circle implements Shape{

  private $radius;

  public function __construct($r){

   $this->radius=$r;

 }

 public function calculateArea(){

  echo 'Area of circle = '.pi()* $this->radius*$this->radius.'<br>';

}

}

class Rectangle implements Shape{

 private $height;

 private $width;

 public function __construct($h,$w){

  $this->height=$h;

  $this->width=$w;

}

public function calculateArea(){

 echo 'Area of a Rectangle=' .$this->height.$this->width.'<br>';

}

}

$circle= new Circle(5);

$rect= new Rectangle(10,20);

$circle->calculateArea();

$rect->calculateArea();

?>