可以添加选项和更改的示例代码。。。检查是否安装了插件。//初始挂钩的附加检查。

add_action(\'admin_init\', \'wpse_73859_init\');
function wpse_73859_init(){
    // if - we in wp-admin
    // if - we class of polylang not found
    // and if we can manage_options (there a lot of different 
    //     capabilities you can use install_plugins for example...)

    if (!class_exists(\'Polylang\') && current_user_can(\'manage_options\')){
        // message function created on a fly... 
        $msg = create_function(\'\', \'echo "<div class=\\"updated\\"><p>require polylang plugin</p></div>";\');
        // and finaly notice! 
        add_action(\'admin_notices\', $msg);
    }
}

// The is_plugin_active() function is only included by default in the admin,
// load it on the front-end too if needed.
if ( ! function_exists(\'is_plugin_active\'))
{
    include_once ABSPATH.\'wp-admin/includes/plugin.php\';
}

// Check if a certain plugin is activated
if ( ! is_plugin_active(\'plugin-directory/plugin-file.php\'))
{
    // It\'s probably too drastic to simply exit, but do whatever you want here
    exit(\'Plugin X requires plugin Y. Please, install plugin Y.\');
}

Codex: is_plugin_active()