PHP Recursive Function to get n generations of x parents - php

Question

I need to return family data (parents, siblings and partners) for 'x' number of generations (passed as $generations parameter) starting from a single person (passed as $id parameter). I can't assume two parents, this particular genealogy model has to allow for a dynamic number of parents (to allow for biological and adoptive relationships). I think my recursion is backwards, but I can't figure out how.
The code below is triggering my base clause 5 times, once for each generation, because $generation is being reduced by 1 not for every SET of parents but for every parent. What I want is for the base clause ($generations == 0) to only be triggered once, when 'x' number of generations for all parents of the initial person are fetched.
public function fetchRelationships($id = 1, $generations = 5, $relationships = array())
{
$perId = $id;
if ($generations == 0) {
return $relationships;
} else {
$parents = $this->fetchParents($perId);
$relationships[$perId]['parents'] = $parents;
$relationships[$perId]['partners'] = $this->fetchPartners($perId);
if (!empty($parents)) {
--$generations;
foreach ($parents as $parentRel) {
$parent = $parentRel->getPer2();
$pid = $parent->getId();
$relationships[$perId]['siblings'][$pid] = $this->fetchSiblings($perId, $pid);
$perId = $pid;
$relationships[$perId] = $this->fetchRelationships($perId, $generations, $relationships);
}
}
return $relationships;
}
}
The methods fetchPartners, fetchParents and fetchSiblings just fetch the matching entities. So I am not pasting them here. Assuming that there are 2 parents, 5 generations and each generation has 2 parents then the return array should contain 62 elements, and should only trigger the base clause once those 62 elements are filled.
Thanks, in advance, for any help.
-----------Edit--------
Have rewritten with fetchSiblings and fetchPartners code removed to make it easier to read:
public function fetchRelationships($id = 1, $generations = 5, $relationships = array())
{
$perId = $id;
if ($generations == 0) {
return $relationships;
} else {
$parents = $this->fetchParents($perId);
$relationships[$perId]['parents'] = $parents;
if (!empty($parents)) {
--$generations;
foreach ($parents as $parentRel) {
$perId = $parentRel->getPer2()->getId();
$relationships[$perId] = $this->fetchRelationships($perId, $generations, $relationships);
}
}
return $relationships;
}
}

Answer 1

Garr Godfrey got it right. $generations will equal zero when it reaches the end of each branch. So you'll hit the "base clause" as many times as there are branches. in the foreach ($parents as $parentRel) loop, you call fetchRelationships for each parent. That's two branches, so you'll have two calls to the "base clause". Then for each of their parents, you'll have another two calls to the "base clause", and so on...
Also, you're passing back and forth the relationships, making elements of it refer back to itself. I realize you're just trying to retain information as you go, but you're actually creating lots of needless self-references.
Try this
public function fetchRelationships($id = 1, $generations = 5)
{
$perId = $id;
$relationships = array();
if ($generations == 0) {
return $relationships;
} else {
$parents = $this->fetchParents($perId);
$relationships[$perId]['parents'] = $parents;
if (!empty($parents)) {
--$generations;
foreach ($parents as $parentRel) {
$perId = $parentRel->getPer2()->getId();
$relationships[$perId] = $this->fetchRelationships($perId, $generations);
}
}
return $relationships;
}
}
you'll still hit the base clause multiple times, but that shouldn't matter.
you might be thinking "but then i will lose some of the data in $relationships", but you won't. It's all there from the recursive returns.

Answer 2

If you're pulling this out of a database, have you considered having the query do all of the leg work for you?
Not sure how you need the data stacked or excluded, but here's one way to do it:
<?php
class TreeMember {
public $id;
// All three should return something like:
// array( $id1 => $obj1, $id2 => $obj2 )
// and would be based on $this->$id
public function fetchParents(){ return array(); }
public function fetchPartners(){ return array(); };
public function fetchSiblings(){ return array(); };
public function fetchRelationships($generations = 5)
{
// If no more to go
if ($generations == 0) { return; }
$branch = array();
$branch['parents'] = $this->fetchParents();
$branch['partners'] = $this->fetchPartners();
$branch['partners'] = $this->fetchSiblings();
// Logic
$generations--;
foreach($branch as $tmType, $tmArr)
{
foreach($tmArr as $tmId => $tmObj)
{
$branch[$tmType][$tmId] =
$mObj->fetchRelationships
(
$generations
)
);
});
return array($this->id => $branch);
}
}