问题是您没有传递任何到mysql_查询的连接
因此,查询没有被查询
$conn = your connection;
$result = mysqli_query($conn,"SELECT * FROM users WHERE email = '$email'") or exit(mysqli_error()); //check for duplicates
$num_rows = mysqli_num_rows($result); //number of rows where duplicates exist
if($num_rows == 0) { //if there are no duplicates...insert
$sql = "INSERT INTO users (name, email, tel, gift, formName, formEmail, formEmirate, birthday, date)
VALUES ('$name', '$email', '$tel','$gift', '$formName', '$formEmail', '$formEmirate','$birthday',CURRENT_TIMESTAMP )";
if (!mysqli_query($conn,$sql))
{
die('Error: ' . mysqli_error());
}
}