php function not returning array in php

Question

I have created a function as below:

<?php
$cat_id=2;
$ids=array();
$ids[]=2;
var_dump(fetchParents($cat_id,$ids));
function fetchParents($cat_id,$ids){
    $db=mysql_connect("localhost","root","") or die("could not connect to database");
    mysql_select_db("symfony",$db) or die("could not connect to symfony database");
    $query="SELECT parent_id FROM categories WHERE id='$cat_id'";
    $result=mysql_query($query,$db);
    if (mysql_num_rows($result)==1) {
        $cat=mysql_fetch_array($result);
        if (isset($cat['parent_id'])) {
             $ids[]=$cat['parent_id'];
             fetchParents($cat['parent_id'],$ids);
        }
        else {
            var_dump($ids);
            return $ids;
        }

    }
    else {
        return $ids;
    }
}
?>

The function should return an array but I am getting null and I m sure $ids is an array. I have also checked using var_dump($ids) inside the function which returns array. Can somebody help me ?

you might want to use a different name for the input $ids and the output $ids — Highmastdon
– Highmastdon, Commented Mar 13, 2013 at 7:40
Also, this can be rewritten to a simple loop - no need to involve a costly recursion. — Vilx-
– Vilx-, Commented Mar 13, 2013 at 7:41

Vilx- · Accepted Answer · 2013-03-13 09:43:08Z

3

There is one control flow that does not perform a return statement before exiting the function. You need to change

fetchParents($cat['parent_id'],$ids);

to

return fetchParents($cat['parent_id'],$ids);

Otherwise after that line the function exits without a return.

Added:

To convert to a loop:

function fetchParents($childId)
{
    $ids = array();

    $db=mysql_connect("localhost","root","") or die("could not connect to database");
    mysql_select_db("symfony",$db) or die("could not connect to symfony database");

    while (true)
    {
        $res = mysql_query("SELECT parent_id FROM categories WHERE id=$childId");
        $row = mysql_fetch_assoc($res);
        if (is_null($row['parent_id']) )
            return $ids;
        $ids[] = $row['parent_id'];
        $childId = $row['parent_id'];
    }
}

Btw - I see that in the original example you also add the ID of the starting element to the array too. If so, then it can be made even more elegant:

function fetchParents($childId)
{
    $ids = array();

    $db=mysql_connect("localhost","root","") or die("could not connect to database");
    mysql_select_db("symfony",$db) or die("could not connect to symfony database");

    while (!is_null($childId))
    {
        $ids[] = $childId;
        $res = mysql_query("SELECT parent_id FROM categories WHERE id=$childId");
        $row = mysql_fetch_assoc($res);
        $childId = $row['parent_id'];
    }
    return $ids;
}

Note that both of these don't handle the case when the SELECT query returns no rows. I assume that that is something that won't happen, since you're selecting by IDs. If however that is a possibility, then you also need to check for $row === false, or you'll get a lot of warning/error messages (not sure what PHP will do in this case).

edited Mar 13, 2013 at 9:43

answered Mar 13, 2013 at 7:39

Vilx-

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3 Comments

Vilx- Over a year ago

@PradipChitrakar - rewrite it as a loop. It will be a LOT simpler, and thus harder to mess up.

rockstar Over a year ago

how can i do this with loop ? any hint. I need to fetch all the parents of a child

Vilx- Over a year ago

@PradipChitrakar - I edited the post, check it out. The idea is simply that at the end of each iteration you set the $childId to $row['parent_id'] and start all over again.

Maks3w · Accepted Answer · 2013-03-13 07:40:10Z

0

If the two first IF are true then the function don't return nothing.

answered Mar 13, 2013 at 7:40

Maks3w

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