标题不适用于条件

Question

I have been trying to get a page working for a number of days now, and there doesn't seem to be much help from the "related" questions on this site.

I have made a signup.php page, which has a form for inputting user credentials to signup up for the site I am building, when the form is filled out and the user presses the 'submit' button, the form uses the action "signupsuccess.php" which has all of the php code for inserting the credentials into the database, and then redirects the user to the "Login.php" page.

My problem: I have written code to say that if the user has not put in any data for one of the fields in the form, then they are brought back to the signup.php page by using this code:

<?php
if(!isset($_POST['fname'])&&($_POST['lname'])&&($_POST['email'])&&($_POST['pass'])){
    header('Location:Signup.php');
    exit;
}
else{
$host = "localhost";
$user = "******";
$password = "******";
$conn = mysql_connect($host, $user, $password);
$db = mysql_select_db('*****', $conn);
if(! get_magic_quotes_gpc() )
{
   $fname = addslashes ($_POST['fname']);
   $lname = addslashes ($_POST['lname']);
   $email = addslashes($_POST['email']);
   $pass = addslashes($_POST['pass']);
}
else
{
   $fname = $_POST['fname'];
   $lname = $_POST['lname'];
   $email = $_POST['email'];
   $pass= $_POST['pass'];
}
$query = mysql_query("select * from users where pass='$pass' AND email='$email'", $conn);
$rows = mysql_num_rows($query);
if ($rows == 1) {
    $errors[] = 'That user already exists, try another email';
}else
{

$sql = "INSERT INTO users ".
       "(fname,lname, pass, email) ".
       "VALUES('$fname','$lname','$pass','$email')";
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
  die('Could not enter data: ' . mysql_error());
}
}
}
mysql_close($conn);

?>

But the header() just won't bring the user back when they haven't put anything in to the fields. Is there anything I am doing obviously wrong or can anyone help me sort out the redirection of the user if they haven't entered anything.

Answer 1

Your if statement is incorrect. If you're just trying to check to see if those variables are set you need to call isset() on all of them.

You can do this with individual calls to isset() or all in one call.

if(!isset($_POST['fname'],$_POST['lname'],$_POST['email'],$_POST['pass'])){
    header('Location:Signup.php');
    exit;
}

FYI, you are wide open to SQL injections. addslashes() does not prevent SQL injections. Also, the mysql_* funcstions are obsolete and you should not be writing new code using them. Look into mysqli or PDO instead.