Unset element from trie using reference

Question

I am having some difficulties to delete empty parent node if empty from a trie. I can correctly identify the node that has the value 3, but then I cannot unset nodes that do not have any children.

What am I missing? Do I have to move to receursive function?

This is my code:

function removeWord($word){
    global $tree;
    $ch=false;
    
    while(strlen($word)>0){
        $p="";
        $parent=&$tree;
        $i=0;
        
        foreach(str_split($word) as $char){
            $i++;
            $p.=$char;
            $parent=&$parent[$char];
            
            if(!$ch && $parent[0]==3 && $p==$word){
                unset($parent[0]);
                $ch=true;
            }
            if($ch && $p==$word){
                if(empty($parent)){
                    unset($parent);
                }
                else{
                    $word="";
                    break;
                }
                $word=substr($word, 0, -1);
            }
        }
    }
}

as example data:

$tree=array("a"=>array("a"=>array()));
$word='aa';

Source:

Array
(
    [a] => Array
        (
            [a] => Array
                (
                    [0] => 3
                )

        )

)

Wrong output:

Array
(
    [a] => Array
        (
            [a] => Array
                (
                )

        )

)

Expected output: Array ( )

Answer 1

Basically I was overwriting the intial value restoring it to the original ocntent, this is the fixed code using recursive function

function removeWord(&$parent,$word){
    
    if(strlen($word)==0){
        if($parent[0]==3){
            unset($parent[0]);
        }

        if(empty($parent)){
            unset($parent);
            return true;
        }
        return false;
    }
    else{
        $char=substr($word, 0, 1);
        $word=substr($word, 1);
        if(removeWord($parent[$char],$word)){
            if(empty($parent[$char])){
                unset($parent[$char]);
                return true;
            }
        }
        return false;
    }
}