改了好久都没改好，郁闷啊
<?
if($usercount==""||$password==""){
echo "<script languge=javascript>alert('请正确输入帐户与密码!');document.location='index.php'</script>";}
else{
session_start();
session_unregister("usercount");
session_unregister("flag");
include "connect.php";
/*这里放检查代码，检查用户输入的合法性*/
$flag=$radiobutton;
//echo $_SESSION["usercount"];
if($flag)
{
$tables="company";
}else
{
$tables="login";
}
$querystr="select * from '$tables' where name='$usercount' and lpw='$password'";
$record=mysql_query($querystr);
$aaa=mysql_num_rows($record);
if($aaa!=0)
{
session_register("usercount");
session_register("flag");
echo "<script languge=javascript>alert('登陆成功!');document.location='index.php'</script>";
}else{
echo "<script languge=javascript>alert('登陆失败!');document.location='index.php'</script>";
}
}
?>