Untitled

<?php

session_start(); // This must always come before any HTML or header data.  ALWAYS, NO EXCEPTIONS.

?>

<!DOCTYPE html>

<html>
<head>
<title>Balance Test</title>
</head>
<body>

<form name ="depositForm" action="index.php" method="post" >
<input name="depositVal" type="text" size="4"/>
<input name"depositSubmit" type="submit" value="Deposit" />
</form>

<?php

if ($_SESSION['balance'] == null) {	// If there's no session data for a balance...
	$_SESSION['balance'] = 0;		// Create that session data
}

if ($_POST && is_numeric($_POST['depositVal'])) {	// Only run this code if there's POST data (ie, the user hit the button already) AND if it's a numeric value
	$_SESSION['balance'] += $_POST['depositVal'];
}

?>

<p>Current Balance:

<?php

echo "$" . $_SESSION['balance'] . ".00";

?>

</p>

</body>
</html>