add to global.php
Code:
//[spoiler]Text[/spoiler]
$s = preg_replace("/\[spoiler\]\s*((\s|.)+?)\s*\[\/spoiler\]\s*/i",
"<b>Spoiler:</b><table border=1 cellspacing=0 cellpadding=3><tr class=spoiler>
<td style='border: 1px black solid'><font color=#000000>\\1</font></td></tr></table>", $s);