如何在同一个类中使用公共函数返回字符串作为变量？ PHP类

I am trying to use a returned string from my function 'get_setting' inside my class name 'settings'. I wanna use the returned string for the variable 'top_banner'. When I try using the '$this' variable to access the function, it does not work.

class settings{

 function get_setting($name, $return="value"){
    $query = mysql_query("SELECT * FROM website_settings WHERE name='".$name."'");
    $row = mysql_fetch_array($query);
    if($row['active'] == false){//This is turned off
        return "disabled";
    }else{//this setting is active
        return $row['value'];
    }

}
    //Values
public $top_banner = $this->get_setting("top_banner");
}

try this:

class settings{

 function get_settings($name, $return="value"){
    $query = mysql_query("SELECT * FROM website_settings WHERE name='".$name."'");
    $row = mysql_fetch_array($query);
    if($row['active'] == false){//This is turned off
        return "disabled";
    }else{//this setting is active
        return $row['value'];
    }

   }
}
  //Values
$my_settings = new settings();
$top_banner = $my_settings->get_settings("top_banner");