Yii2默认界面增加多级菜单

Yii 2.0.6

参考：http://blog.youkuaiyun.com/zhongyuan_1990/article/details/31789541

在css中，增加：

        .dropdown-submenu {
            position: relative;
        }
        .dropdown-submenu > .dropdown-menu {
            top: 0;
            left: 100%;
            margin-top: -6px;
            margin-left: -1px;
            -webkit-border-radius: 0 6px 6px 6px;
            -moz-border-radius: 0 6px 6px;
            border-radius: 0 6px 6px 6px;
        }
        .dropdown-submenu:hover > .dropdown-menu {
            display: block;
        }
        .dropdown-submenu > a:after {
            display: block;
            content: " ";
            float: right;
            width: 0;
            height: 0;
            border-color: transparent;
            border-style: solid;
            border-width: 5px 0 5px 5px;
            border-left-color: #ccc;
            margin-top: 5px;
            margin-right: -10px;
        }
        .dropdown-submenu:hover > a:after {
            border-left-color: #fff;
        }
        .dropdown-submenu.pull-left {
            float: none;
        }
        .dropdown-submenu.pull-left > .dropdown-menu {
            left: -100%;
            margin-left: 10px;
            -webkit-border-radius: 6px 0 6px 6px;
            -moz-border-radius: 6px 0 6px 6px;
            border-radius: 6px 0 6px 6px;
        }

修改vendor\yiisoft\yii2-bootstrap\Dropdown.php

在

return Html::tag('ul', implode("\n", $lines), $options);

前面增加一行

$options['class'] = 'dropdown-menu';

这样会在菜单的ul里面增加一个css，可实现多级菜单。