Undefined index in php? - php

Question

I am trying to get the value from a textbox in another page I created and the textbox is automatically set to 0 but it keeps on telling me that the index is undefined? but once you click the confirm button the value gets submitted but I want it to automatically set as 0 without having to click the button.
This is page1:
<?php
if(isset($_POST['topscart']))
{
$_SESSION['topscart']=$_POST['topscart'];
print"<script language=javascript>
window.location='ACCOUNT.php';
</script>";
}
?>
This is page 2:
<td>No. of Female Tops Ordered: </td>
<td><center><?php
print" ".$_SESSION['topscart'];
?>
</td>
Textbox Code in page 1:
No. of Female Tops in Your Cart: <input type="text" value="0" size="10" name="topscart" id="topscart" >
Total: <input text="text" size="10" value="0" name="topstotal" id="topstotal" >
<input type ="submit" value="Confirm Order"></button>
<input type ="reset" id="topsbutton2" name="topsbutton2" value="Cancel Order"></button>
</center>

Answer 1

I couldn't quite understand the purpose but you must click the button to populate the $_POST variable.
If you must, set the value to 0 and automatically get it in $_POST then you need to use JS also - on page load fill-up the "topscart" with 0, and use .click() of the button.
Hope this helps

Answer 2

<?php
if(isset($_POST['topscart']))
{
session_start();
$_SESSION["topscart"] = $_POST['topscart'];
print"<script language=javascript>
window.location='ACCOUNT.php';
</script>";
}
?>
2nd page
<?php
session_start();
echo $_SESSION["topscart"];
?>

Answer 3

I think you want to default the session value to 0 unless it is set by the initial form? If that is the case then update the code on page 1 to:
<?php
if(isset($_POST['topscart']))
{
$_SESSION['topscart']=$_POST['topscart'];
print"<script language=javascript>
window.location='ACCOUNT.php';
</script>";
} else {
$_SESSION['topscart'] = 0;
}