这个例子可能并不实用，但基本概括了面向对象的三个特征：继承性，封装性，多态性。本例的主要功能有：
效果如下：
思路:
需要改进的地方：
index.php代码如下：
<span> 1</span> <html>
<span> 2</span> <head>
<span> 3</span> <meta http-equiv="charset" content="utf-8">
<span> 4</span> </head>
<span> 5</span> <body>
<span> 6</span> <div id="center">
<span> 7</span> <h1>图形周长面积计算器</h1>
<span> 8</span> <!--点击链接的时候使用GET传递图形的形状属性给index.php,也就是页面本身-->
<span> 9</span> <a href="index.php?shape=rect">矩形</a>
<span>10</span> <a href="index.php?shape=triangle">三角形</a>
<span>11</span> <a href="index.php?shape=circle">圆形</a>
<span>12</span> </div>
<span>13</span> <div id="inputForm">
<span>14</span> <?<span>php
</span><span>15</span> <span>/*</span><span>自动加载类</span><span>*/</span>
<span>16</span> <span>function</span> __autoload(<span>$className</span><span>){
</span><span>17</span> <span>include</span> (<span>strtolower</span>(<span>$className</span>).'.class.php'<span>);
</span><span>18</span> <span> }
</span><span>19</span>
<span>20</span> <span>/*</span>
<span>21</span> <span> 1.先new一个Form对象，发现没有form类的定义，把类名Form传递到自动加载类的函数参数进行类的自动加载。
</span><span>22</span> <span> 2.echo一个对象的引用，会调用该对象的__toString方法返回一个字符串，echo输出的就是对象返回的字符串，
</span><span>23</span> <span> 这里输出一个表单等待用户的输入。
</span><span>24</span> <span>*/</span>
<span>25</span> <span>echo</span> <span>new</span> Form("index.php"<span>);
</span><span>26</span>
<span>27</span> <span>/*</span><span>如果用户点击了提交按钮，自动加载result类，输出结果</span><span>*/</span>
<span>28</span> <span>if</span>(<span>isset</span>(<span>$_POST</span>["sub"<span>])){
</span><span>29</span> <span>echo</span> <span>new</span><span> result();
</span><span>30</span> <span> }
</span><span>31</span> ?>
<span>32</span> </div>
<span>33</span> </body>
<span>34</span> </html>form.class.php代码如下：
<span> 1</span> <?<span>php
</span><span> 2</span> <span>/*</span>
<span> 3</span> <span> project:面向对象版图形计算器
</span><span> 4</span> <span> file:form.class.php
</span><span> 5</span> <span> description:对不同的图形输出不同的表单
</span><span> 6</span> <span>*/</span>
<span> 7</span> <span>class</span><span> form{
</span><span> 8</span> <span>private</span> <span>$formAction</span>=<span>NULL</span>; <span>//</span><span>保存响应表单的文件</span>
<span> 9</span> <span>private</span> <span>$shape</span>=<span>NULL</span>; <span>//</span><span>保存图形的形状</span>
<span>10</span>
<span>11</span> <span>/*</span>
<span>12</span> <span> @param string $action 对象初始化传入的参数，代表响应的页面的是哪一个文件
</span><span>13</span> <span>*/</span>
<span>14</span> <span>function</span> __construct(<span>$action</span> = ""<span>){
</span><span>15</span> <span>$this</span>->formAction = <span>$action</span>; <span>//</span><span>把传入的参数保存到$formAction中；</span>
<span>16</span> <span>$this</span>->shape = <span>isset</span>(<span>$_GET</span>["shape"]) ? <span>$_GET</span>["shape"]:"rect"; <span>//</span><span>从表单传递的变量中获取图形类别，如没有传递，默认为矩形</span>
<span>17</span> <span> }
</span><span>18</span> <span>function</span><span> __toString(){
</span><span>19</span> <span>$form</span> = '<form action="'.<span>$this</span>->formAction.'?shape='.<span>$this</span>->shape.'" method="post">'<span>;
</span><span>20</span> <span>//</span><span>下面两行使用变量函数调用对应图形的私有函数，返回input部分表单的字符串</span>
<span>21</span> <span>$shape</span> = 'get'.<span>ucfirst</span>(<span>$this</span>-><span>shape);
</span><span>22</span> <span>$form</span> .= <span>$this</span>-><span>$shape</span><span>();
</span><span>23</span>
<span>24</span> <span>$form</span> .= '</br><input type="submit" name="sub" value="计算"/></br>'<span>;
</span><span>25</span> <span>$form</span> .= '</form>'<span>;
</span><span>26</span>
<span>27</span> <span>return</span> <span>$form</span><span>;
</span><span>28</span> <span> }
</span><span>29</span> <span>//</span><span>私有方法，返回矩形表单input部分的字符串；</span>
<span>30</span> <span>private</span> <span>function</span><span> getRect(){
</span><span>31</span> <span>//</span><span>在表单提交后输入的内容继续显示，防止其消失</span>
<span>32</span> <span>$formheight</span>=<span>isset</span>(<span>$_POST</span>['height']) ? <span>$_POST</span>['height'] : <span>NULL</span><span>;
</span><span>33</span> <span>$formwidth</span>=<span>isset</span>(<span>$_POST</span>['width']) ? <span>$_POST</span>['width'] : <span>NULL</span><span>;
</span><span>34</span> <span>$input</span> = '<p>请输入矩形的长和宽</p>'<span>;
</span><span>35</span> <span>$input</span> .= '矩形的高度：<input type="text" name="height" value="'.<span>$formheight</span>.'"/><br></br>'<span>;
</span><span>36</span> <span>$input</span> .= '矩形的宽度：<input type="text" name="width" value="'.<span>$formwidth</span>.'"/></br>'<span>;
</span><span>37</span> <span>return</span> <span>$input</span><span>;
</span><span>38</span> <span> }
</span><span>39</span> <span>//</span><span>返回三角形输入表单input部分的字符串</span>
<span>40</span> <span>private</span> <span>function</span><span> getTriangle(){
</span><span>41</span> <span>//</span><span>在表单提交后继续显示出来，防止其消失</span>
<span>42</span> <span>$formside1</span>=<span>isset</span>(<span>$_POST</span>['side1']) ? <span>$_POST</span>['side1'] : <span>NULL</span><span>;
</span><span>43</span> <span>$formside2</span>=<span>isset</span>(<span>$_POST</span>['side2']) ? <span>$_POST</span>['side2'] : <span>NULL</span><span>;
</span><span>44</span> <span>$formside3</span>=<span>isset</span>(<span>$_POST</span>['side3']) ? <span>$_POST</span>['side3'] : <span>NULL</span><span>;
</span><span>45</span> <span>$input</span> = '<p>请输入三角形的三边</p>'<span>;
</span><span>46</span> <span>$input</span> .= '边长1：<input type="text" name="side1" value="'.<span>$formside1</span>.'" /></br></br>'<span>;
</span><span>47</span> <span>$input</span> .= '边长2：<input type="text" name="side2" value="'.<span>$formside2</span>.'"/></br></br>'<span>;
</span><span>48</span> <span>$input</span> .= '边长3：<input type="text" name="side3" value="'.<span>$formside3</span>.'"/></br>'<span>;
</span><span>49</span> <span>return</span> <span>$input</span><span>;
</span><span>50</span> <span> }
</span><span>51</span> <span>//</span><span>返回圆形表单input部分的字符串</span>
<span>52</span> <span>private</span> <span>function</span><span> getCircle(){
</span><span>53</span> <span>$formradius</span>=<span>isset</span>(<span>$_POST</span>['radius']) ? <span>$_POST</span>['radius'] : <span>NULL</span>; <span>//</span><span>在输入表单提交后内容继续显示出来，防止其消失</span>
<span>54</span> <span>$input</span> = '<p>请输入半径</p>'<span>;
</span><span>55</span> <span>$input</span> .= '半径：<input type="text" name="radius" value="'.<span>$formradius</span>.'"/></br>'<span>;
</span><span>56</span> <span>return</span> <span>$input</span><span>;
</span><span>57</span> <span> }
</span><span>58</span> <span> }
</span><span>59</span> result.class.php代码如下：
<span> 1</span> <?<span>php
</span><span> 2</span> <span>class</span><span> result{
</span><span> 3</span> <span>private</span> <span>$shape</span> = <span>NULL</span><span>;
</span><span> 4</span>
<span> 5</span> <span>//</span><span>使用GET传递的变量，实例化一个相应的对象，返回一个对象的引用；</span>
<span> 6</span> <span>function</span><span> __construct(){
</span><span> 7</span> <span>$this</span>->shape = <span>new</span> <span>$_GET</span>["shape"<span>]();
</span><span> 8</span> <span> }
</span><span> 9</span> <span>//</span><span>调用对象的属性和方法，返回周长和面积</span>
<span>10</span> <span>function</span><span> __toString(){
</span><span>11</span> <span>$result</span> = <span>$this</span>->shape->shapeName.'的周长为'.<span>$this</span>->shape->perimeter().'</br>'<span>;
</span><span>12</span> <span>$result</span> .= <span>$this</span>->shape->shapeName.'的面积为'.<span>$this</span>->shape->area().'</br>'<span>;
</span><span>13</span> <span>return</span> <span>$result</span><span>;
</span><span>14</span> <span> }
</span><span>15</span> } 抽象类shape.class.php代码如下：
<span> 1</span> <?<span>php
</span><span> 2</span> <span>/*</span>
<span> 3</span> <span> project:面向对象版图形计算器
</span><span> 4</span> <span> file:shape.class.php
</span><span> 5</span> <span> description:抽象类，定义两个抽象方法area()和perimeter(),以及定义方法validate对输入的值进行验证
</span><span> 6</span> <span>*/</span>
<span> 7</span> <span>abstract</span> <span>class</span><span> shape{
</span><span> 8</span> <span>public</span> <span>$shapeName</span>; <span>//</span><span>形状名称；</span>
<span> 9</span> <span>abstract</span> <span>function</span> area(); <span>//</span><span>抽象类area(),让子类去实现，体现多态性</span>
<span>10</span> <span>abstract</span> <span>function</span> perimeter(); <span>//</span><span>抽象类perimeter();</span>
<span>11</span>
<span>12</span> <span>/*</span>
<span>13</span> <span> @param mixed $value 接受表单输入值
</span><span>14</span> <span> @param string $message 提示消息前缀
</span><span>15</span> <span> @param boolean 返回值，成功为TRUE，失败为FALSE
</span><span>16</span> <span>*/</span>
<span>17</span> <span>protected</span> <span>function</span> validate(<span>$value</span>,<span>$message</span> = "输入的值"<span>){
</span><span>18</span> <span>if</span>(<span>$value</span> < 0 || <span>$value</span> == <span>NULL</span> || !<span>is_numeric</span>(<span>$value</span><span>)){
</span><span>19</span> <span>$message</span> = <span>$this</span>->shapeName.<span>$message</span><span>;
</span><span>20</span> <span>echo</span> '<font color="red">'.<span>$message</span>.'必须为正数</font><br>'<span>;
</span><span>21</span> <span>return</span> <span>FALSE</span><span>;
</span><span>22</span> <span> }
</span><span>23</span> <span>else</span>
<span>24</span> <span>return</span> <span>TRUE</span><span>;
</span><span>25</span> <span> }
</span><span>26</span> }子类triangle.class.php代码如下：
<span> 1</span> <?<span>php
</span><span> 2</span> <span>/*</span><span>*
</span><span> 3</span> <span> project:面向对象版图形计算器
</span><span> 4</span> <span> file:triangle.class.php
</span><span> 5</span> <span> description：继承抽象类shape，计算并返回三角形的周长和面积
</span><span> 6</span> <span>*/</span>
<span> 7</span> <span>class</span> triangle <span>extends</span><span> shape{
</span><span> 8</span> <span>private</span> <span>$side1</span> = 0; <span>//</span><span>边长1；</span>
<span> 9</span> <span>private</span> <span>$side2</span> = 0; <span>//</span><span>边长2；</span>
<span>10</span> <span>private</span> <span>$side3</span> = 0; <span>//</span><span>边长3；</span>
<span>11</span>
<span>12</span> <span>/*</span>
<span>13</span> <span> 构造函数：对表单变量进行合理性验证，通过则初始化三个边长
</span><span>14</span> <span>*/</span>
<span>15</span> <span>function</span><span> __construct(){
</span><span>16</span> <span>$this</span>->shapeName = "三角形"; <span>//</span><span>命名图形
</span><span>17</span>
<span>18</span> <span> //使用父类的方法validate检查输入的是否为正数</span>
<span>19</span> <span>if</span>(<span>$this</span>->validate(<span>$_POST</span>["side1"],"边长1") & <span>$this</span>->validate(<span>$_POST</span>["side2"],"边长2") & <span>$this</span>->validate(<span>$_POST</span>["side3"],"边长3"<span>)){
</span><span>20</span>
<span>21</span> <span>//</span><span>使用私有方法验证两边和是否大于第三边</span>
<span>22</span> <span>if</span>(<span>$this</span>->validatesum(<span>$_POST</span>["side1"],<span>$_POST</span>["side2"],<span>$_POST</span>["side3"<span>])){
</span><span>23</span> <span>$this</span>->side1 = <span>$_POST</span>["side1"]; <span>//</span><span>若通过验证初始化三边；</span>
<span>24</span> <span>$this</span>->side2 = <span>$_POST</span>["side2"<span>];
</span><span>25</span> <span>$this</span>->side3 = <span>$_POST</span>["side3"<span>];
</span><span>26</span> <span> }
</span><span>27</span> <span>else</span><span>{
</span><span>28</span> <span>echo</span> '<font color="red">两边的和要大于第三边</font>'<span>;
</span><span>29</span> <span>exit</span><span>();
</span><span>30</span> <span> }
</span><span>31</span> <span> }
</span><span>32</span> <span>else</span><span>{
</span><span>33</span> <span>exit</span><span>();
</span><span>34</span> <span> }
</span><span>35</span> <span> }
</span><span>36</span> <span>/*</span><span>使用海伦公式计算面积,并返回结果</span><span>*/</span>
<span>37</span> <span>function</span><span> area(){
</span><span>38</span> <span>$s</span> = (<span>$_POST</span>["side1"] + <span>$_POST</span>["side2"] + <span>$_POST</span>["side3"])/2<span>;
</span><span>39</span> <span>return</span> <span>sqrt</span>(<span>$s</span> * (<span>$s</span> - <span>$_POST</span>["side1"]) * (<span>$s</span> - <span>$_POST</span>["side2"]) * (<span>$s</span> - <span>$_POST</span>["side3"<span>]));
</span><span>40</span> <span> }
</span><span>41</span> <span>/*</span><span>计算并返回周长</span><span>*/</span>
<span>42</span> <span>function</span><span> perimeter(){
</span><span>43</span> <span>return</span> <span>$_POST</span>["side1"] + <span>$_POST</span>["side2"] + <span>$_POST</span>["side3"<span>];
</span><span>44</span> <span> }
</span><span>45</span> <span>/*</span><span>计算三角形两边和是否大于第三边，是返回TRUE，否返回FALSE</span><span>*/</span>
<span>46</span> <span>private</span> <span>function</span> validatesum(<span>$side1</span>,<span>$side2</span>,<span>$side3</span><span>){
</span><span>47</span> <span>if</span>((<span>$side1</span> + <span>$side2</span>) > <span>$side3</span> && (<span>$side1</span> + <span>$side3</span>) > <span>$side2</span> && (<span>$side2</span> + <span>$side3</span>) > <span>$side1</span><span>)
</span><span>48</span> <span>return</span> <span>TRUE</span><span>;
</span><span>49</span> <span>else</span>
<span>50</span> <span>return</span> <span>FALSE</span><span>;
</span><span>51</span> <span> }
</span><span>52</span> }子类circle.class.php代码如下：
<span> 1</span> <?<span>php
</span><span> 2</span> <span>/*</span>
<span> 3</span> <span> project:面向对象的图形计算器
</span><span> 4</span> <span> file:circle.class.php
</span><span> 5</span> <span> description:接收表单值，返回周长和面积
</span><span> 6</span> <span>*/</span>
<span> 7</span> <span>class</span> circle <span>extends</span><span> shape{
</span><span> 8</span> <span>private</span> <span>$radius</span>; <span>//</span><span>圆的半径
</span><span> 9</span>
<span>10</span> <span> //初始化圆的名称，检查输入合法性并初始化半径</span>
<span>11</span> <span>function</span><span> __construct(){
</span><span>12</span> <span>$this</span>->shapeName = "圆形"<span>;
</span><span>13</span> <span>if</span>(<span>$this</span>->validate(<span>$_POST</span>["radius"],"半径"<span>))
</span><span>14</span> <span>$this</span>->radius = <span>$_POST</span>["radius"<span>];
</span><span>15</span> <span> }
</span><span>16</span> <span>//</span><span>返回圆的面积</span>
<span>17</span> <span>function</span><span> area(){
</span><span>18</span> <span>return</span> 3.14 * <span>$this</span>->radius * <span>$this</span>-><span>radius;
</span><span>19</span> <span> }
</span><span>20</span> <span>//</span><span>返回圆的周长</span>
<span>21</span> <span>function</span><span> perimeter(){
</span><span>22</span> <span>return</span> 3.14 * 2 * <span>$this</span>-><span>radius;
</span><span>23</span> <span> }
</span><span>24</span> }子类rect.class.php代码如下：
<span> 1</span> <?<span>php
</span><span> 2</span> <span>/*</span>
<span> 3</span> <span> project:面向对象的图形计算器
</span><span> 4</span> <span> file:rect.class.php
</span><span> 5</span> <span> descrition:声明一个矩形资料，实现形状抽象类计算周长和面积的方法，返回矩形的周长和面积
</span><span> 6</span> <span>*/</span>
<span> 7</span> <span>class</span> rect <span>extends</span><span> shape{
</span><span> 8</span> <span>private</span> <span>$width</span>; <span>//</span><span>矩形的宽度</span>
<span> 9</span> <span>private</span> <span>$height</span>; <span>//</span><span>矩形的高度
</span><span>10</span>
<span>11</span> <span> //使用父类的validate方法验证输入的合法性，通过则初始化宽度和高度</span>
<span>12</span> <span>function</span><span> __construct(){
</span><span>13</span> <span>$this</span>->shapeName = "矩形"<span>;
</span><span>14</span> <span>if</span>(<span>$this</span>->validate(<span>$_POST</span>["width"],"宽度") && <span>$this</span>->validate(<span>$_POST</span>["height"],"高度"<span>)){
</span><span>15</span> <span>$this</span>->width = <span>$_POST</span>["width"<span>];
</span><span>16</span> <span>$this</span>->height = <span>$_POST</span>["height"<span>];
</span><span>17</span> <span> }
</span><span>18</span> <span> }
</span><span>19</span> <span>//</span><span>返回面积</span>
<span>20</span> <span>function</span><span> area(){
</span><span>21</span> <span>return</span> <span>$this</span>->width * <span>$this</span>-><span>height;
</span><span>22</span> <span> }
</span><span>23</span> <span>//</span><span>返回周长</span>
<span>24</span> <span>function</span><span> perimeter(){
</span><span>25</span> <span>return</span> 2 * (<span>$this</span>->width + <span>$this</span>-><span>height);
</span><span>26</span> <span> }
</span><span>27</span> }声明：
1.本文只适合实验，不适合现实应用，若造成不良后果，本人概不负责。
2.本文为原创博客，可以在个人平台自由转载，但需要注明出处，附上链接，否则视为盗用。严禁用于商业用途，如有需要，联系本人支付稿费，授权后方能使用。
