main.html

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>двачик</title>
    <!-- Latest compiled and minified CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css">
    <!-- Optional theme -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap-theme.min.css">
</head>
<body>
    <header>
        <div class="container">
            <div class="row">
                <div class="col-sm-3 col-xs-12"></div>
                <div class="col-sm-6 col-xs-12">
                    <form accept-charset="UTF-8" action="index.php" method="post">
                        <div class="input-group">
                            <input type="text" name="search" class="form-control" placeholder="Пошук">
                            <span class="input-group-btn">
                                <button class="btn btn-default" type="submit"><span class="glyphicon glyphicon-search" aria-hidden="true"></span></button>
                            </span>
                        </div>
                    </form>
                    <div class="col-sm-3 col-xs-12"></div>
                </div>
            </div>
        </div>
    </header>

    <h1><?= htmlspecialchars($searchField) ?></h1>

    <!-- jQuery (necessary for Bootstrap's JavaScript plugins) -->
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
    <!-- Latest compiled and minified JavaScript -->
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
</body>
</html>