Attempted Fix

<?php

include 'config.php';

// user input
$page    = isset( $_GET['page'] ) ? (int) $_GET['page'] : 1;
$perPage = isset( $_GET['per-page'] ) && $_GET['per-page'] <= 50 ? (int) $_GET['per-page'] : 5;

// positioning
$start = ( $page > 1 ) ? ( $page * $perPage ) - $perPage : 0;

// query
$articles = $conn->prepare( "SELECT SQL_CALC_FOUND_ROWS * FROM articles LIMIT {$start}, {$perPage}" );
$articles->execute();
$articles = $articles->fetchAll( PDO::FETCH_ASSOC );

// pages
$total = $conn->query( "SELECT FOUND_ROWS() as total" )->fetch()['total'];
$pages = ceil( $total / $perPage );

?>

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <!-- Latest compiled and minified CSS -->
        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
        <!-- Latest compiled and minified JavaScript -->
        <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
        <!--custom css-->
        <link rel="stylesheet" type="text/css" href="style.css">
        <title>php pagination</title>
    </head>
    <body>
        <div class="container">
            <div class="col-md-12">
                <?php foreach ( $articles as $article ): ?>
                <div class="article">
                    <p class="lead">
                        <?php echo $article['id']; ?>: <?php echo $article['title']; ?>
                    </p>
                </div>
                <?php endforeach ?>
            </div>
            <div class="col-md-12">
                <div class="well well-sm">
                    <div class="paginate">
<ul class="pagination">
<?php for ( $x=1; $x <= $pages; $x++ ): ?>
    <?php $currentStyle = ($x === $page) ? 'class="page-selected"' : ''; ?>
    <li>
        <a <?= $currentStyle ?> href="?page=<?php echo $x; ?>&per-page=<?php echo $perPage; ?>"><?= $x ?></a>
    </li>
<?php endfor; ?>
</ul>
                    </div>
                    </div>
                </div>
            </div>
        </div><!--end main container-->
    </body>
</html>