php案列

<center>
<form id="form1" name="form1" method="post" action="">
    <select name="select">
      <option value="">请选择一个表</option>
      <option>student</option>
      <option>sc</option>
      <option>course</option>
    </select>
    <input type="submit" name="Submit" value="确定" />
</form>
</center>
<?php
if (isset($_REQUEST["Submit"]))
{
   $bm=$_REQUEST["select"];
   $con=mysqli_connect('localhost','root','','stu'); //连接服务器
   
   mysqli_query($con,"SET NAMES utf8");
   $sql="select * from $bm";
   $result=mysqli_query($con,$sql);  //执行SQL语句
   $row=mysqli_fetch_row($result);
   echo "<table width='400' border='1' align='center' cellpadding='0'>";
   echo "<tr>";
   for ($i=0; $i<mysqli_num_fields($result); $i++)
     echo "<td  align='center' height='30'>".mysqli_fetch_field_direct($result,$i)->name."</td>";
   echo "</tr>";
   while($row)
   {
      echo "<tr>";
      for ($i=0; $i<mysqli_num_fields($result); $i++)
         echo "<td  align='center' height='30'>".$row[$i]."</td>";
      echo "</tr>"; 
      $row=mysqli_fetch_row($result);  
   }
   echo "</table>";
}
?>