header.php

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- The above 3 meta tags *must* come first in the head; any other head content must come *after* these tags -->
    <meta name="description" content="">
    <meta name="author" content="">
    <!--<link rel="icon" href="../../favicon.ico">-->

    <!-- Custom styles for this template -->
    <link href="css/jumbotron-narrow.css" rel="stylesheet">

    <title>MFF Game</title>
    <!-- Latest compiled and minified CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">

    <!-- Optional theme -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap-theme.min.css">

	<!-- Bootstrap needs jquery -->
	<script src="https://code.jquery.com/jquery-1.11.3.min.js"></script>
    <!-- Latest compiled and minified JavaScript -->
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
    <!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->
    <!--[if lt IE 9]>
    <script src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script>
    <script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
    <![endif]-->
</head>
<body>

<div class="container">
    <div class="header clearfix">
        <nav>
            <ul class="nav nav-pills pull-right">
                <li role="presentation" <?php echo isCurrent('index.php')  ? 'class="active"' : null; ?>><a href="index.php">Home</a></li>
	            <li role="presentation" <?php echo isCurrent('oldGame.php')  ? 'class="active"' : null; ?>><a href="game.php">Old game</a></li>
                <li role="presentation" <?php echo isCurrent('game.php')  ? 'class="active"' : null; ?>><a href="game.php">Game</a></li>
	            <li role="presentation"><a href="plain-game.html">Game without PHP</a></li>
            </ul>
        </nav>
        <h3 class="text-muted">MFF Game</h3>
    </div>

<?php
function isCurrent($page) {
	return endsWith($_SERVER['PHP_SELF'], $page);
}

function endsWith($haystack, $needle) {
	return $needle === "" || (($temp = strlen($haystack) - strlen($needle)) >= 0 && strpos($haystack, $needle, $temp) !== FALSE);
}
?>