Convert a php variable to session variable

I am having problem setting a variable in PHP for multiple use into if statements.

Although there are many files in my layout but these are the 3 files relevant to this issue:

session.php (it is actually a JavaScript function which determines the browser-width of the visitor which is included in my javascript file and I call this via an ajax call. However since that is irrelevant to this issue hence to avoid confusion and too much code on this page I am avoiding that file.)

<?php
    session_start();
    $_SESSION['layoutType'] = $_REQUEST['layoutType'];  
?>

core.php

<?php
    session_start();
    if (empty($_SESSION['layoutType'])) {
        echo '<script type="text/javascript"> var session=false; var layoutType;</script>';
    } else {
        echo '<script type="text/javascript"> var session=true; var layoutType=' . $_SESSION['layoutType'] . ';</script>';
    }

    $layout = 'normal';

    if (!empty($_SESSION['layoutType'])) {
       $layoutType = $_SESSION['layoutType'];
       if ( $layoutType <= 219 ) {
          $layout = 'minimal';
       } else if ($layoutType >= 220 && $layoutType <= 1024 ) {
          $layout = 'small';
       } else {
          $layout = 'normal';
       }
    $_SESSION['layout'] = $layout;

    }

index.php

<?php
include ('core/core.php');


// Function to load all the JavaScript files

getJS();

echo '<div>Your browser width is: ' . $_SESSION['layoutType'] . ' and Value of $layout variable currently is <strong>'.$layout.'</strong></div>'; 

if ($layout = 'normal') { ?>

    <?php echo '<strong>' . $layout . '</strong> is the value of $layout in session'; ?>

    <div id="sidebar">
    <p>Widgets go here</p>
    </div>

<?php } ?>

The output

Even though, The layout-width falls in the small category (Your browser width is: 872 and Value of $layout variable currently is small), it is still displaying the bit which it should display only is the layout-widthe category is normal (normal is the value of $layout in session).

Typically what is hapenning here is the value of $layout is being overwritten by the if statement in the index.php file.

What I am looking for?

Along with layoutType I also want the value of $layout to be set in the session based on the logic in core.php. So that I can use it multiple times across the website in various if statements.

This is very important because these are varioys widgets / content in my layout which I want to load / not-load depending on the device of my visitor. Hence almost all the widhets wil be wrapped into an if statement.

Kindly help.