The {if} statement is MUCH easier, and it is always better to edit the templates than mess with the PHP
To hide the left column for the product detail page, you would use this:
{if $main ne "product"}
column code here
{/if}
You can use multiple {if} statements to hide it from different pages...for example, if you want to also hide it from the cart:
{if $main ne "cart" and $main ne "product"}
column code
{/if}