parent=指定栏目ID
parent=0或省略
parent={sort:pcode} 可用于输出当前栏目的同级菜单
parent={sort:scode} 可用于输出当前栏目的子菜单
parent={sort:tcode} 可用于输出当前栏目顶级菜单的子菜单
scode=1,2,3 用于控制输出栏目范围

{pboot:nav}                   
[nav:link]
[nav:name]

{pboot:if([nav:soncount]>0)}
{pboot:2nav parent=[nav:scode]}
[2nav:link]
[2nav:name]

{pboot:2if([2nav:soncount]>0)}
{pboot:3nav parent=[2nav:scode]}
[3nav:link]
[3nav:name]
{/pboot:3nav}
{/pboot:2if}


{/pboot:2nav}
{/pboot:if}

{/pboot:nav}