A preco nepouzijes pole (array)?
Inac okrem toho co uz pisali vyssie mozes si vytvorit aj inu variable napr.
$temporary_variable = "new".$category."_01";
a potom pouzit
$$temporary_variable = blablabla
http://de.php.net/manual/en/language.variables.var iable.php
Ale to co chces moze byt potencialne bezpecnostne riziko. Nauc sa robit s poliami.