Potrzebuje małej pomocy z klasami Opcje

[Raven1122]

Witam,

Mam takie klasy:

[PHP] pobierz, plaintext 
<?php
require_once("config.php");
class mysql{
 
	public function __construct(){
		$db = new PDO('mysql:host='.HOST.';dbname='.DB.'', USERNAME, PASSWORD);
		$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
	}
 
}
 
class sb extends mysql{
 
	public function shout($author, $shout){
		$this->author = $author;
		$this->shout = $shout;
		$this->data = date("Y-m-d H:i:s");
		$this->olddata = date("Y-m-d H:i:s", time()-7*24*60);
 
		//$stmt = $db->prepare("DELETE FROM isb_shouts WHERE sdate < ?");
		//$stmt->bindValue(1, $this->olddata);
		//$stmt->execute();
 
		$stmt = $db->prepare("INSERT INTO isb_shouts(sid, author, sdate, shout) VALUES(?, ?, ?, ?, ?)");
		$stmt->bindValue(1, '');
		$stmt->bindValue(2, $this->author);
		$stmt->bindValue(3, $this->data);
		$stmt->bindValue(4, $this->author);
		$stmt->execute();
	}
 
	public function fetchshouts(){
		$stmt = $db->prepare("SELECT * FROM isb_shouts");
		$stmt->execute();
		while($row = $stmt->fetch()){
			if(EMOTICONS == 1){
				$emot = $db->prepare("SELECT * FROM isb_emoticons");
				$emot->execute();
 
				while($emots = $emot->fetch()){
					$emot_sign = $emots['emoticon_sign'];
					$emot_image = "<img src='".$emots['emoticon_image']."' />";
					str_replace($emot_sign, $emot_image, $row['shout']);
				}
			}
			if(SBCODE == 1){
				$sbcode = $db->prepare("SELECT * FROM isb_sbcode");
				$sbcode->execute();
 
				while($code = $sbcode->fetch()){
					$code_sign = $sbcode['code'];
					$code_html = $sbcode['codehtml'];
					str_replace($code_sign, $code_html, $row['shout']);
				}
			}
			if(CENSURE == 1){
				$censure = $db->prepare("SELECT * FROM isb_censore");
				$censure->execute();
 
				while($word = $censure->fetch()){
					$word_tocensore = $word['word'];
					$word_replecement = $word['replacement'];
					str_replace($word_tocensore, $word_replecement, $row['shout']);
				}
			}
		}
		return $row['author'];
		return $row['sdate'];
		return $row['shout'];
	}
 
}
 
 
?>
[PHP] pobierz, plaintext 

I teraz takie pytanie:
Jak wykorzystać $db w klasie dziedziczącej po mysql?? mam na myśli sb