每次我第一次留下任何未填充的文本框时，它都会注册到数据库中，就像我将所有文本框都留空一样，但是当你第二次（两者中的任何一个）这样做时，那将是时间会弹出警告框...我不知道该怎么做。请帮帮我。这是我的代码：
<?php
ini_set('display_errors', 0);
$email= $_POST['email'];
$user= $_POST['user'];
$password= $_POST['password'];
$image =($_FILES['image']['name']);
$submit= $_POST['submit'];
if (empty($email) || empty($password) || empty($user) )
{
echo "<script type='text/javascript'>
alert('You did not complete all of the required fields');
window.location='blah2.php';
</script>";
}
if(isset($submit))
{
$con = mysqli_connect("localhost", "root", "", "top")
or die('error in connection'.mysqli_connect_error());
$q = "SELECT username , email FROM registries WHERE username = ? OR email = ?";
$stmt = mysqli_prepare ($con, $q);
mysqli_stmt_bind_param($stmt, 'ss', $user, $email);
mysqli_stmt_execute($stmt);
mysqli_stmt_bind_result($stmt, $user , $email);
mysqli_stmt_store_result($stmt);
$result = mysqli_stmt_num_rows($stmt);
if($result > 0)
{
echo "<script type='text/javascript'>
alert('Email address or Username is already taken. Please pick another one.');
window.location='blah2.php';
</script>";
}
else
{
$q="INSERT INTO registries VALUES (?,?,?,?)";
$stmt = mysqli_prepare($con, $q);
move_uploaded_file($_FILES["image"]["tmp_name"],"uploads/" . $_FILES["image"]["name"]);
mysqli_stmt_bind_param($stmt, 'ssss', $email, $user, $password, $image);
mysqli_stmt_execute($stmt);
mysqli_stmt_store_result($stmt);
mysqli_stmt_close($stmt);
header('Location: blah.php');
}
}