PHP session shopping cart problem

[nepoverljiv]

I have one code which I use to add articles in shopping cart. In another website working without any kind of problem, but on new one he makes me problem, he add me double article in shopping cart. I press once “add to basket” but he put me twice that articles. When I press “add to basket” I calling this code to found out which articles is:

PHP Code:

<?php
    session_start();   
    $var=$_SERVER['REQUEST_URI']; //reading 
    $id = substr(strrchr($var, "korpa?"),6 );//reading first element after  "?"
    $tbl_name="description"; //table name

    $_SESSION['korpa']+=$row[price];      

    if($_SESSION['numproduct']==0){
        $_SESSION['articles']=array($id);
        $_SESSION[numproduct]++;
    }else{
        array_push($_SESSION['articles'],$id);
        $_SESSION[numproduct]++;
    }

    redirect("javascript: history.go(-1)");
?>

On main page I using this code to see what exist in shopping cart:

PHP Code:

$i=0;
$tbl_name="description";
$query = count($_SESSION['articles']);

if($query==0){
    echo "Your shopping cart is empty.";
}else{
    echo "In your shopping cart exist:<br/><br/>";
    for($i=0;$i<=$query-1;$i++){
    $br=$i+1;

connect();

    $element=$_SESSION['articles'][$i];
    $sql="SELECT * FROM $tbl_name WHERE id=$element";
    $subject_set=mysql_query($sql);
    $subject=mysql_fetch_array($subject_set);

    echo "   ".$br.". ";
    echo $subject['name'];
    echo " - <b>".$subject['prices']." USD</b><br/>  "; 
}

echo "<p align=right><a href=index.php?=order class=basket>Order</a> &middot; <a href=includes/delete.php>Delete items</a></p>"; 


Does anyone knows why articles goes twice in shopping cart?

[nepoverljiv]

I have figured it out that problem is in this line of code:

PHP Code:

   $sql="SELECT * FROM $tbl_name WHERE id=$element";
    $subject_set=mysql_query($sql);
    $subject=mysql_fetch_array($subject_set); 


Everything before is ok, but here give me double values. Please help me

[nepoverljiv]

I can't believe, no one to even try.

[AndrewGSW]

Originally Posted by nepoverljiv

I can't believe, no one to even try.

Returning to the previous page

redirect("javascript: history.go(-1)");

will cause a duplicate form-submission.

Session variables are initially strings, so it should really be:

PHP Code:

if($_SESSION['numproduct']=='0'){ 


assuming that the numproduct's are cleared (unset) at some stage.