TP5 显示未定义数组索引:child 错误

在制作tp5的时候显示未定义数组索引如何解决呢？

{volist name="navData" id="vo"}

<div>

<h3>{$vo.cat_name}</h3>

<div>

{volist name="vo.child" id="vi"}

<dl>

<dt>{$vi.cat_name}</dt>

<dd>

{volist name="vi.child" id="vp"}

{$vp.cat_name}

{/volist}

</dd>

</dl>

{/volist}

</div>

</div>

{/volist}

原因是某些数组没有child字段
解决办法 :加个判断如果没有child字段就赋予其空值

public function getNavData()

{

$return = array();

$allData = db('category')->select();

foreach ($allData as $k => $v)

{

if ($v['pid'] == 0)

{

if (!isset($v['child'])){

$v['child'] = array();

}

foreach ($allData as $k1 => $v1)

{

if ($v1['pid'] == $v['id'])

{

if (!isset($v1['child']))

{

$v1['child'] = array();

}

foreach ($allData as $k2 => $v2)

{

if ($v2['pid'] == $v1['id'])

{

$v1['child'][] = $v2;

}

}

$v['child'][] = $v1;

}

}

$return[] = $v;

}

}

return $return;

}

PS : tp5中通过模型select返回的是对象通过db select返回的是数组