Recursion? Tree...

[mattih5]

Hi,

I'm trying to create an array from a larger array which will get all parent categories up to the top most category.

In this example the category I want to retrieve the relationships for is 182.

My query returns the following:

array (
  100 => '0',
  101 => '0',
  102 => '0',
  103 => '0',
  104 => '0',
  107 => '0',
  109 => '107',
  111 => '0',
  131 => '0',
  132 => '0',
  178 => '0',
  179 => '178',
  180 => '179',
  181 => '179',
  182 => '181',
)

As the array shows 182 has a parent of 181, 181 has a parent of 179, 179 has a parent of 180 and 180 is the top-most category.

I'm struggling to write a function which pulls out this relationship from the rest and displays it.

[mattih5]

I realise I could call and SQL function on each parent ID but I don't want to do this due to the amount of DB calls that could occur.

[guido2004]

You could use a recursive function (didn't test it):

function getChain($array, $value) {
  $result = $array[$value] . ' ';
  if ($array[$value] <> '0') {
    $result .= getChain($array, $array[$value]);
  }
}
 
$array = array (
  100 => '0',
  101 => '0',
  102 => '0',
  103 => '0',
  104 => '0',
  107 => '0',
  109 => '107',
  111 => '0',
  131 => '0',
  132 => '0',
  178 => '0',
  179 => '178',
  180 => '179',
  181 => '179',
  182 => '181',
);
$value = 182;
echo getChain($array, $value);

[mattih5]

Thanks, looks good but how can I return the relationship back into an array? So it returns something like:

$aRelations[182]=181
$aRelations[181]=179
$aRelations[179]=178
$aRelations[178]=0 

[guido2004]

function getChain($array, $value) {
  $result[$value] = $array[$value];
  if ($array[$value] <> '0') {
    $result = $result + getChain($array, $array[$value]);
  }
  return $result
}

Forgot the return...

[AnthonySterling]

Off Topic:

I really must remember you can use the addition operator on arrays. Despite seeing it many times, it always seems to be a revelation when I see it again.

[guido2004]

Off Topic:

I really must remember you can use the addition operator on arrays. Despite seeing it many times, it always seems to be a revelation when I see it again.

Yeah, me too
I was looking for a way to add a value to the beginning of the array without losing numeric key values (array_unshift), and the second user comment gave me this illuminating tip

[mattih5]

Great, that works perfect, I'll do some further testing with different scenarios. Thanks.