How to access variable value from another php script - php

Question

I have read so many pages and am stuck on this for the past three hours now because it just won't work.
I keep getting Notice: Undefined index: firstname
here is the bulk of the segment that isn't working:
$errMsg = "";
function sanitise($data){
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
if (isset($_POST["firstname"]))
{
$firstname = $_POST["firstname"];
$firstname = sanitise($firstname);
if (!preg_match("/^[A-Za-z \-]+$/",$firstname))
{
$errMsg .= "First name must contain only letters or hyphens.<br/>";
}
if (strlen($firstname) > 40)
{
$errMsg .= "First name cannot be over 40 characters long.<br/>";
}
} else {
$errMsg .= "First name cannot be empty.<br/>";
$firstname = "";
}
if ($errMsg != "")
{
header("Location: fix_order.php?firstname=$firstname");
}
this is the code on fix_order.php where I want to access the variables.
$firstname = $_GET["firstname"];
echo "<p>firstname is $firstname .</p>";
I have tested the $firstname on the first page and it echo's the values just fine.

Answer 1

change your code to
$firstname = $_GET["errMsg"];
echo "<p>firstname is $firstname .</p>";
You can't access $firstname as this is the value not the key. errMsg is the key you should use.

Answer 2

Looks fine to me, it should work.
To get rid of the notice, you need to define variable by using isset()
$firstname = isset($_GET['firstname']) ? $_GET['firstname'] : '';
OR
if(isset($_GET['firstname'])) {
$firstname = $_GET['firstname'];
} else {
$firstname = '';
}