mysql_query("RENAME TABLE `lss_messages` TO `newname`");

$prefix = "lss_";
$new_prefix = "pbb_";
$tables = mysql_query("SHOW TABLES");
while ( $table = mysql_fetch_array($tables) )
{
	if ( strstr($table[0],$prefix) )
	{
		$new_name = str_replace($prefix,$new_prefix,$table[0]);
		mysql_query("RENAME TABLE `".$table[0]."` TO `".$new_name."`");
	}
}