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Detailed explanation of return value of infinite classification recursive function in ecshop

伊谢尔伦Original: 2017-06-27 09:28:351573browse

When doing product classification in the secondary development of ecshopindex, the top-level category id must be obtained based on the category id. The first reaction was to use recursion to pass it out, so I wrote the recursive function as follows:

function getCatTopId($cat_id)
{
    if ($cat_id)
    {
      $res = Array();
        $sql = &#39;SELECT cat_id, parent_id&#39;
             . &#39; FROM &#39; . $GLOBALS[&#39;ecs&#39;]->table(&#39;category&#39;) 
             . &#39; WHERE cat_id = &#39; . $cat_id . &#39; AND is_show = 1&#39;;
        $res = $GLOBALS[&#39;db&#39;]->getAll($sql);
        if ($res[0][&#39;parent_id&#39;] > 0)
        {
            getCatTopId($res[0][&#39;parent_id&#39;]);
        }
        else
        {
            return $res[0][&#39;cat_id&#39;];
        }
    }
    else
    {
        return 1;
    }
}

A test program, no return value? After checking for a long time, no error was found. It seemed that the circuit in the brain was broken. When I asked Shui Shen (a kind-hearted netizen) today, he helped me answer it, and the modification is as follows:

function getCatTopId($cat_id)
{
    if ($cat_id)
    {
     $res = Array();
        $sql = &#39;SELECT cat_id, parent_id&#39;
             . &#39; FROM &#39; . $GLOBALS[&#39;ecs&#39;]->table(&#39;category&#39;) 
             . &#39; WHERE cat_id = &#39; . $cat_id . &#39; AND is_show = 1&#39;;
        $res = $GLOBALS[&#39;db&#39;]->getAll($sql);
        if ($res[0][&#39;parent_id&#39;] > 0)
        {
            return getCatTopId($res[0][&#39;parent_id&#39;]); // 修改处，多写个 return ，让函数返回值
        }
        else
        {
            return $res[0][&#39;cat_id&#39;];
        }    }
    else
    {
        return 1;
    }
}

The function is written internally. Even if it returns, it only returns to the position of the internal function, so there is still There is a main function, which must be returned again

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