使自定义php“爆炸”函数递归

I know http_build_query() and parse_str() are a better solution for this sort of problem but I can't change the structure of the data in the particular project I'm working on so I'm trying to simplify things a little by creating large 3d associative arrays from a database stored string.

Can someone please give me a hand making this function recursive? I want it to take something like this:

explode3D( $separators = array('|',','),
$string = "val1,val2|val1,val2,val3",
$keys = "cat1,item1,item2|cat2,item1,item2,item3"
);

And return something like this

Array (
'cat1' => Array('item1'=>'val1', 'item2'=>'val2'),
'cat2' => Array('item1'=>'val1', 'item2'=>'val2', 'item3'=>'val3')
)

Here's the function so far:

function explode3D($separators,$string,$keys=0){
    $res = array();

    if(is_array($separators)){//MULTI DIMENSION MODE: (unfinished!!)

        //help needed here//

    }else{//SINGLE DIMENSION MODE:
        $vals = explode($separators,$string);
        if($keys === 0){ //NO KEYS:
            $res = $vals;
        }else if($keys === 1){//ALTERNATE ROWS ARE KEYS:
            $key = '';
            for($i=0; $i<sizeof($vals); $i++){
                if ($i++ % 2 == 1 ){ //every second element:
                    $key = $vals[$i]; //save the key
                }else{
                    $res[$key] = $vals[$i]; //set the saved key = value
                }
            }
        }else{ //GET KEYS FROM $keys ARRAY:
            if(is_string($keys)){ //explode keys string if necessary (using $separators)
                $keys = explode3D($separators,$keys);
            }
            for($i=0; $i<sizeof($vals); $i++){
                $res[$keys[$i]] = $vals[$i];
            }
        }
    }
    return($res);
}

Here's the idea how it supposed to work. I believe there are few typos and missed operators, but it hopefully helps you to understand how-to.

<?php
$string = "val1,val2|val1,val2,val3";
$keys = "cat1,item1,item2|cat2,item1,item2,item3";

$firstDimension = explode("|", $keys);
$firstDimensionValues = explode("|", $string);
$newArray = Array();
for($i = 0; $i < count($firstDimension); $i++)
{
  $d2Keys = explode(",", $firstDimension[$i]);
  $key = $d2Keys[0];
  array_shift($d2Keys); // remove $key
  $d2Values = explode(",", $firstDimensionValues[$i]);
  for ($a = 0; $a < count($d2Keys); $a++)
  {
    $newArray[$key][$d2Keys[$a]] = $d2Values[$a];
  }
}

print_r($newArray);