//rect.class.php
php
    abstract class Shape{
        public $name;
        abstract function area();
        abstract function view();
        abstract function test($arr);
    }
?>

//index.php







 
 

class="box">
    
图形计算器
    

        矩形
        三角形
    
    
    php
        error_reporting(E_ALL & ~E_NOTICE);
        function __autoload($classname){
            include strtolower($classname).".class.php";
        }
        if(!empty($_GET['action'])) {
            $classname = ucfirst($_GET['action']);
            $shape=new $classname($_POST);
            $shape->view();
            if(isset($_POST['dosubmit'])) {
                if($shape->test($_POST)) {
                    echo $shape->name."的面积为：".$shape->area()."
";
                }
            }
        }else{
            echo "请选择一个要计算的图形!
";
        }
    ?>

//rect.class.php
php
class Rect extends Shape{
    private $width;
    private $height;
    function __construct($arr=[]){
        if(!empty($arr)){
            $this->width = $arr['width'];
            $this->height = $arr['height'];
        }
        $this->name = "矩形";
    }
    function area() {
        return $this->width * $this->height;
    }
    function view() {
        $form = '
';
        $form .=$this->name.'的宽:
';
        $form .=$this->name.'的高:
';
        $form .='
';
        $form .='
';
        echo $form;
    }
    function test($arr) {
        $bg = true;
        if($arr['width'] < 0) {
            echo $this->name."的宽不能小于0!
";
            $bg = false;    
        }
        if($arr['height'] < 0) {
            echo $this->name."的高度不能小于0!
";
            $bg = false;
        }
        return $bg;
    }
}
?>

//triangle.class.php
php
class Triangle extends Shape{
    private $b1;
    private $b2;
    private $b3;
    function __construct($arr=[]){
        if(!empty($arr)){
            $this->b1 = $arr['b1'];
            $this->b2 = $arr['b2'];
            $this->b3 = $arr['b3'];
        }
        $this->name = "三角形";
    }
    function area() {
        $p = ($this->b1 + $this->b2 + $this->b3)/2;
        return sqrt($p*($p-$this->b1)*($p-$this->b2)*($p-$this->b3));
    }
    function view() {
        $form = '
';
        $form .=$this->name.'第一个边的宽:
';
        $form .=$this->name.'第二个边的宽:
';
        $form .=$this->name.'第三个边的宽:
';
        $form .='
';
        $form .='
';
        echo $form;
    }
    function test($arr) {
        $bg = true;
        if($arr['b1'] < 0) {
            echo "第一个边的宽不能小于0!
";
            $bg = false;    
        }
        if($arr['b2'] < 0) {
            echo "第二个边的宽不能小于0!
";
            $bg = false;    
        }
        if($arr['b3'] < 0) {
            echo "第三个边的宽不能小于0!
";
            $bg = false;    
        }
        if(($arr['b1'] + $arr['b2'] < $arr['b3'])||($arr['b1'] + $arr['b3'] < $arr['b2'])||($arr['b3'] + $arr['b2'] < $arr['b1'])){
            echo '两边之和不能小于第三边
';
            $bg = false;
        }
        return $bg;
    }
}
?>