index_prev is used to display the previous loop index.
on the first loop, this is set to -1.
Example 7-22. section property index_prev
{section name=customer loop=$custid}
{$smarty.section.customer.index} id: {$custid[customer]}<br>
{* FYI, $custid[customer.index] and $custid[customer] are identical in meaning *}
{if $custid[customer.index_prev] ne $custid[customer.index]}
The customer id changed<br>
{/if}
{/section}
OUTPUT:
0 id: 1000<br>
The customer id changed<br>
1 id: 1001<br>
The customer id changed<br>
2 id: 1002<br>
The customer id changed<br>