Recursive PHP function is returning unexpected array - php

Question

I have a hierarchical data that I put in a array that I call $dt. Than I have a array that store the relationship between these data that I call $in. I have create a function that has as parameter, the initial index, level, array $dt an the array $in. I was debugging the function but I am not find why the subclass is lost during the process. The complete code is:
$dt = array(
41=>array( "pk"=>41,"parentPk"=>30,"name"=>"car1"),
15=>array("pk"=>15,"parentPk"=>11,"name"=>"food" ),
70=>array("pk"=>70,"parentPk"=>30,"name"=>"car3" ),
18=>array("pk"=>18,"parentPk"=>15,"name"=>"food1" ),
49=>array("pk"=>49,"parentPk"=>30,"name"=>"car2" ),
20=>array( "pk"=>20,"parentPk"=>15,"name"=>"food2"),
30=>array("pk"=>30,"parentPk"=>11,"name"=>"car" )
);
echo "<pre>";
print_r($dt);
echo "</pre>";
$in=array(11=>array(15,30),15=>array(18,20),30=>array(41,49,70));
echo "<pre>";
print_r($in);
echo "</pre>";
function fn_tree($parent_id, $level,$dt,$in) {
if(is_null($parent_id)){
$parent_id ="NULL";
}
if (isset($in[$parent_id])) {
foreach ($in[$parent_id] as $id) {
$pk=$in[$parent_id];
$arrEnd[$id]=str_repeat("-", $level*2) .$dt[$id]["name"];
fn_tree($id, $level + 1,$dt,$in,$arrEnd);
}
}
return $arrEnd;
}
$arrEcho = fn_tree(11, 0, $dt, $in);
echo "<br>";
echo "result";
echo "<br>";
echo "<pre>";
print_r($arrEcho);
echo "</pre>";
$desired = array(
15=>"food",
18=>"food1",
20=>"food2",
30=>"car",
41=>"car1",
49=>"car2",
70=>"car3"
);
echo "<br>";
echo "desired";
echo "<br>";
echo "<pre>";
print_r($desired);
echo "</pre>";
So why the function is losting the sub-classes?
Output is:
Array data
(
[41] => Array
(
[pk] => 41
[parentPk] => 30
[name] => car1
)
[15] => Array
(
[pk] => 15
[parentPk] => 11
[name] => food
)
[70] => Array
(
[pk] => 70
[parentPk] => 30
[name] => car3
)
[18] => Array
(
[pk] => 18
[parentPk] => 15
[name] => food1
)
[49] => Array
(
[pk] => 49
[parentPk] => 30
[name] => car2
)
[20] => Array
(
[pk] => 20
[parentPk] => 15
[name] => food2
)
[30] => Array
(
[pk] => 30
[parentPk] => 11
[name] => car
)
)
Array relationship
(
[11] => Array
(
[0] => 15
[1] => 30
)
[15] => Array
(
[0] => 18
[1] => 20
)
[30] => Array
(
[0] => 41
[1] => 49
[2] => 70
)
)
result
Array
(
[15] => food
[30] => car
)
desired
Array
(
[15] => food
[18] => food1
[20] => food2
[30] => car
[41] => car1
[49] => car2
[70] => car3
)

Answer 1

The clue to your problem is/should have been "Undefined variable: arrEnd." If you aren't running in an environment where you can see this warning, you should try to set up such an environment. If you are running in such an environment, you should play close attention to this and all other warnings.
I'm not sure if it is the convention here to just give a clue or a whole answer, but proceeding on to give a fairly complete answer: it seems that you intended to pass arrEnd in by reference, but did not pass it in at all.
Also, I'm a little confused by your desired output. Don't you in fact desire something with double dashes showing hierarchy, as below?
Array
(
[15] => food
[18] => --food1
[20] => --food2
[30] => car
[41] => --car1
[49] => --car2
[70] => --car3
)