目前本人只会一个用户:
$username = $_POST["username"];
$pwd = $_POST["password"];
if($username!=null){
$sql = "select * from admin where username='$username'";
$sth = mysqli_query($conn, $sql);
$result = mysqli_fetch_all($sth,MYSQLI_ASSOC);
$row = mysqli_fetch_array($sth1);
print_r($row[0]);
//for($a=0;$a<=)
if($pwd == $result[0]["userpwd"]){
echo "<script>window.location.href='admin_index.php' </script>";
}
else{
echo "<script>alert('密码错误')</script>";
}
}