php修改更新数据库用户记录的函数

$link_id = mysql_connect("localhist","root","qwaszx") or die("连接失败！");
if($link_id)
{
 mysql_select_db("my_test");
 if(!$_GET[id])
 {
  $result = mysql_query("select * from userinfo");
  echo "<TABLE border = 1>
   <TR>
   <TD>编号</TD>
   <TD>用户名称</TD>
   <TD>性别</TD>
   <TD>年龄</TD>
   <TD>注册时间</TD>
   <TD>操作</TD>
   </TR>";
  while($row = mysql_fetch_array($result))
  {
   echo "<TR>
    <TD>".$row[id]."</TD>
    <TD>".$row[uername]."</TD>
    <TD>".$row[gender]."</TD>
    <TD>".$row[age]."</TD>
    <TD>".$row[regdate]."</TD>
    <TD><a href = modify.php?id = ".$row[id].">编辑</a></TD>
    </TR>";
  }
  echo "</TABLE>";
 }else
 {
  if(!$_POST[ok])
  {
   $sql = "select * frim userinfo where id = ".$_GET[id];
   $result = mysql_query($sql);
   $row = mysql_fetch_array($result);
   ?>
            <form method = post action = 'modify.php?id = <? echo $_GET[id];?>'>
            <?
   echo $row[id]."<br>";
   ?>
            <INPUT TYPE = "hidden" name = "id" value = <? echo $row[id];?>>
            姓名 <input type = text name = "uername" value = <? echo $row[uername];?>><br>
            性别 <input type = text name = "gender" value = <? echo $row[gender];?>><br>
            年龄 <input type = text name = "age" value = <? echo $row[age];?>><br>
            注册时间 <input type = text name = "regdate" value = <? echo $row[regdate];?>><br>
            <input type = submit name = ok value = "提交">
            </form>
            <?
  }else
  {
   $sql = "update userinfo set username = '".$_POST[username]."',gender = '".$_POST[gender]."',age = '".$_POST[age]."',regdate = '".$_POST[regdate]."'where id = '".$_POST[id]."'";
   $result = mysql_query($sql);
   if($result)
    echo "记录已经成功修改<br>"<a href = 'modify.php'>继续修改记录</a>;
   else
    echo "记录修改失败<br><a href = modify.php?id = ".$_POST[id].">返回</a>";
  }
 }
}