Putting a session in a if and else statement - php

Question

I've got a problem with putting a session to store some page info into a variable
heres the code:
<?php
$t = $_GET['nm'];
if ($t=="1")
{
session_start();
// store session data
$_SESSION['nm']=1;
}
else
{
?>
<script>
if( /Android|webOS|iPhone|iPad|iPod|BlackBerry/i.test(navigator.userAgent) ) {
window.location = "http://www.gouda-info.nl/mobile";
}
</script>
<?php
}
$session = $_SESSION['nm'];
if ($session=="1")
{
When i try to use the script it just doesn't work. I use this script to redirect mobile users, but if they choose to use the Desktop version they'll be allowed by activating the session that stores if the user has activated the desktop version by putting nothing or a 1 in the link like so:
http://www.example.com/index.php?nm=1
hope anyone comes up with a bright solution. :)
EDIT:
it just fails if i try to run this code, it gives me a blank page.

Answer 1

session must be started on the top, and sometimes you deal with == 1 and other with $t == "1"
try this code:
// first line
session_start();
$t = $_GET['nm'];
if ($t == 1) { // use 1 instead of "1"
// store session data
$_SESSION['nm'] = 1;
} else {
?>
<script>
if (/Android|webOS|iPhone|iPad|iPod|BlackBerry/i.test(navigator.userAgent)) {
window.location = "http://www.gouda-info.nl/mobile";
}
</script>
<?php
}
$session = $_SESSION['nm'];
if ($session == 1) { // use 1 instead of "1"
}

Answer 2

You are using js code in php, but your js will be run after entire php file executed. So use php instead;
<?php
session_start();
$t = $_GET['nm'];
if ($t == "1") {
// store session data
$_SESSION['nm'] = "1";
} else {
if(isMobile()) {
header('Location: http://www.gouda-info.nl/mobile');
exit();
}
}
$session = $_SESSION['nm'];
if ($session == "1") {
......
}
function isMobile($user_agent=NULL) {
if(!isset($user_agent)) {
$user_agent = isset($_SERVER['HTTP_USER_AGENT']) ? $_SERVER['HTTP_USER_AGENT'] : '';
}
return (strpos($user_agent, 'Android') !== FALSE
|| strpos($user_agent, 'webOS') !== FALSE
|| strpos($user_agent, 'iPhone') !== FALSE
|| strpos($user_agent, 'iPad') !== FALSE
|| strpos($user_agent, 'iPod') !== FALSE
|| strpos($user_agent, 'BlackBerry') !== FALSE);
}