I have a cart.php webpage, which, on open, has a SESSION variable $_SESSION['userid']. After calling echo include 'header.php';, that variable is unset.
header.php:
<html>
<head>
<meta charset="UTF-8">
<title></title>
<link href="../stylesheets/stylesheet.css" rel="stylesheet" type="text/css">
</head>
<body>
<?php
// session_start();
?>
<div class="headerClass">
<div >
<img src="images/logo.jpg" id="logoId"/>
</div>
<div class="nameClass">
ShopAholics
</div>
<div class="myCart" onclick="window.open('cart.php')">
<button type="button">My Cart</button>
</div>
<div class="myAccount">
<button type="button" onclick="window.open('accountActivities.php')">My Account</button>
</div>
<div class="logout">
<button type="button" onclick="<?php if(isset($_SESSION))unset($_SESSION['userid']);?>">Logout</button>
</div>
</div>
</body>
</html>
If i try to add the commented line, evey time that is called a new session is issued. Why is that?
UPDATE: i tried adding session_start in the beginning of header.php, now every time it starts a new session; also, i already have a session_start in the cart.php, which works just fine.