regexp

			function parser_tagow($wynik) {
				global $pelny_url;
				return '<a href\''.$pelny_url.'postboard/tag/'.$wynik[0].'\'>'.$wynik[0].'</a>';
			}

			$tresc = $mysqli -> real_escape_string($_POST['tresc']);
			$tresc = preg_replace_callback('/\#[a-zA-Z0-9]+/', 'parser_tagow', $tresc);
			echo $tresc;

in:
#aaa asdasdsadsadasd12321321 #bbb adsdasd #ccc asdasdasa #a1a1a1 ............

out:
http://screencloud.net/v/6z4j