title: php: click the submit button but it dosen't work
body: <p>This website say I can't put too many code. So I put these pictures for intance.</p>
  
  <p><a href="https://i.stack.imgur.com/BJZA5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BJZA5.png" alt="enter image description here"></a>
  <a href="https://i.stack.imgur.com/Gwi2I.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Gwi2I.png" alt="enter image description here"></a>
  <a href="https://i.stack.imgur.com/hqAlE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hqAlE.png" alt="enter image description here"></a></p>
  
  <pre class="lang-java prettyprint-override"><code>&lt;form name="form1" method="post" action='doAction.php?option=add&amp;a=&lt;?php echo $_GET["id"]?"update&amp;id=".$_GET["id"]:"add";?&gt;'&gt;
                          &lt;table width="820px" height="500px" border="0" cellpadding="0" bgcolor="#FFFFFF"&gt;
                              &lt;tr&gt;
                                  &lt;td width="500px" align="center" style="font-size:20px;line-height: 100px"&gt;&lt;div&gt;公告主题：&lt;/div&gt;&lt;/td&gt;
                                  &lt;td width="500px" height="50px"&gt;
                                      &lt;input name="title" type="text" id="txt_title" size="40"
                                             style="width: 500px; height: 50px"
                                             value="&lt;?php
                                      $result = null;
                                      if ($id = $_GET['id']) {
                                          //1.导入配置文件和Model类
                                          require("config.php");
                                          require("Model.php");
                                          $mod = new Model('tb_notice');                     //实例化类
                                          $result = $mod-&gt;find($id);                         //调用find()方法
                                          echo $result['title'];                         //读取标题字段
                                      }?&gt;"&gt;
                                  &lt;/td&gt;
                              &lt;/tr&gt;
                              &lt;tr&gt;
                                  &lt;td height="500px" align="center" style="font-size: 20px"&gt;公告内容：&lt;/td&gt;
                                  &lt;td&gt;&lt;textarea name="content" cols="60" rows="40" style="width: 500px; height: 400px;margin: 0px;"
                                                id="txt_content" value="&lt;?php echo $result['content']?&gt;"&gt;&lt;/textarea&gt;&lt;/td&gt;
                              &lt;/tr&gt;
                              &lt;tr&gt;
                                  &lt;td height="40" colspan="2" align="center"&gt;
                                      &lt;input  type="submit" name="Submit" id="Submit" value="修改/添加"&gt;
                                      &amp;nbsp;&lt;input type="reset" name="Submit2" id="Submit2" value="重置"&gt;&lt;/td&gt;
                              &lt;/tr&gt;
                          &lt;/table&gt;
                      &lt;/form&gt;
  </code></pre>
  
  <p><strong>when I clicked the submit button, it didn't work. But when I clicked the reset button , it works.</strong></p>
  
  <p><strong>Here is a animation.</strong> 
  <a href="https://i.stack.imgur.com/C9Xbl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/C9Xbl.png" alt="enter image description here"></a>
  <a href="https://i.stack.imgur.com/iLwhN.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iLwhN.gif" alt="enter image description here"></a></p>
  
  <p><strong>Do I need to submit any other information?</strong></p>
  
  <p>===update===</p>
  
  <p>when I changed:</p>
  
  <pre><code>&lt;form name="form1" method="post" action="doAction.php?option=add&amp;a=&lt;?php if ($_GET['id']) {
      echo "update&amp;id=$_GET[id]";
      } else {
          echo "add";
      } ?&gt;"&gt;
  </code></pre>
  
  <p><strong>TO:</strong></p>
  
  <pre><code>&lt;form name="form1" method="post" action="doAction.php?option=add&amp;a=add"&gt;
  </code></pre>
  
  <p>It works.</p>
  
  <p>Why?
  <a href="https://i.stack.imgur.com/aVrQR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aVrQR.png" alt="enter image description here"></a></p>