// [ codebox]Some long text[/codebox ]
		$s = preg_replace(
	'/\[codebox\]\s*((\s|.)+?)\s*\[\/codebox\]\s*/i',
	'<div class="codetop">CODEBOX</div><div class="codemain" style="width: 100%">\\1</div>', $s );

.codetop{
	background: #f1b000 url(http://www.ru-board.com/new/images/topics/php.gif) no-repeat right;
	color: #000;
	font-weight: bold;
	margin: 0 auto 0 auto;
	padding: 3px;
}
 
.codemain{
	background: #FFF;
	border: 1px solid #000;
	color: #000;
	margin: 0 auto 0 auto;
	padding: 3px;
}