将CSS从HTML更改为'；s在PHP中

我在php中通过回显HTML元素；我想更改那个html的css，但没有成功。我想知道你能不能这样做？

PHP

                }  else {
                    include("steamauth/SteamConfig.php");
                    include('steamauth/userInfo.php'); //To access the $steamprofile array
                    //Protected content
                    echo '<div class="dropdown">';
                    echo '<a class="dropdown-toggle" href="#">';
                    echo '<img src="'.$steamprofile['avatar'].'" height="30" style="border-radius: 100%;">';
                    echo '</a>';
                    echo '<div class="dropdown-content">';
                    echo '<a class="logout" href="'.$steamauth['logoutpage'].'"</a>';
                    echo '</div>';                  
                    echo '</div>';
                } 

CSS

.dropdown-content {
display: none;
position: absolute;
background-color: #f9f9f9;
min-width: 160px;
box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
}
.dropdown-content a:hover {background-color: #f1f1f1}
.dropdown-toggle:hover .dropdown-content {
     display: block;
}
.dropdown-toggle:hover .dropbtn {
    background-color: #3e8e41;
}