php表单插入数据库，求大神帮忙

Question

<?php  
    if(!isset($_POST['submit'])){  
        //如果没有表单提交，显示一个表单  
?>  
    <form action="" method="post">  
   <table>
        <tr>
          <td>请输入姓名：<input type="text" name="username"></td>
        </tr>

        <tr>
          <td>请输入电话：    <input type="text" name="mobile"></td>
        </tr>

        <tr>
          <td>请确认城市：    <input type="text" name="city"></td>
        </tr>

        <tr>
          <td>请输入邮箱：<input type="text" name="emile"></td>
        </tr>

        <tr>
          <td><input type="submit" value="报名">    <input type="reset" value="重置"></td>

        </tr>
      </table>
    </form>  
<?php  
    }  
    else  
    {  
        //如果提交了表单  
        //数据库连接参数  
        $host = "localhost";  
        $user = "root";  
        $pass = "";  
        $db = "anxinjia";  

        //取得表单中的值，检查表单中的值是否符合标准，并做适当转义，防止SQL注入
         $username=$_POST['username'];
  $mobile=$_POST['mobile'];
  $city=$_POST['city'];
   $emile=$_POST['emile'];  


        //打开数据库连接  
        $connection = mysql_connect($host, $user, $pass) or die("Unable to connect!");  

        //选择数据库  
        mysql_select_db($db) or die("Unable to select database!");  

        //构造一个SQL查询  
        $query = "INSERT INTO shuipf_AttractInvestment(username, mobile, city,emile) VALUES('$username', '$mobile', '$city','$emile')";  

        //执行该查询  
        $result = mysql_query($query) or die("Error in query: $query. ".mysql_error());  

        //插入操作成功后，显示插入记录的记录号  
        echo "记录已经插入， mysql_insert_id() = ".mysql_insert_id();  

        //关闭当前数据库连接  
        mysql_close($connection);  
    }  
?>

Answer 1

参考PHP MySQL Insert Into
在你的mysql_select_db($db)和mysql_query($query) 都加上$connection,即

mysql_select_db($db， $connection)
mysql_query($query, $connection)