如何通过变量引导模态弹出窗口？

Question

I am studying the bootstrap, and follow the example:

<button class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
    Shows the modal
</button>

<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="false">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal" aria-hidden="true">
                    &times;
                </button>
                <h4 class="modal-title" id="myModalLabel">
                    模态框（Modal）标题
                </h4>
            </div>
            <div class="modal-body">
                在这里添加一些文本
            </div>
            <div class="modal-footer">
                <button type="button" class="btn btn-default" data-dismiss="modal">关闭
                </button>
                <button type="button" class="btn btn-primary">
                    提交更改
                </button>
            </div>
        </div><!-- /.modal-content -->
    </div><!-- /.modal -->
</div>

if I click the button the modal will popup, but I don't understand which variable is controlling the modal popup and disappear.

I want to through a variable to popup it. there is a requirement.

when I enter a Smarty page, if the page do not exists a access_token variable, I want the modal popup automatically.

So, how to realize in this example?