php - functions to get/set values in multidimensional arrays dynamically

Question

I am trying to write a shoping cart in php and I have a problem with get/set values in multidimentional arrays. I keep the current order in $_SESSION['basket']. It looks like that:

[basket] => Array
        (
            [0] => Array
                (
                    [pid] => 3
                    [name] => Camera
                    [price] => 200.99
                    [quantity] => 1

                )

            [1] => Array
                (
                    [pid] => 5
                    [name] => Computer
                    [price] => 320.99
                    [quantity] => 1

                    [extras] => Array
                        (
                            [0] => Array
                                (
                                    [pid] => 86
                                    [name] => RAM
                                    [price] => 99
                                    [qty] => 1
                                )

                            [1] => Array
                                (
                                    [pid] => 98
                                    [name] => CD-ROM
                                    [price] => 19.99
                                    [qty] => 1
                                )

                        )

                )
 )

Every item is stored as a subarray. I have a function, which checks if a given item exists in the basket array and returns the path to it. For example, if I want to check for a product with id 98 (CD-Rom), the function returns the following path: 1:extras:1.

I cant figure out how to use the path if I want to get or a set a value in the array. Is it possible to construct the path to an array key, without the use of eval()? I have these functions:

 function get_val($array, $path, $key) {
    //some code
    return eval('return '.$array.$path.$key.';');
 }

So, $price = get_val($_SESSION['basket'], $path, 'price'); should return the price for CD-ROM (19.99)

 function set_val($array, $path, $key, $value) {
    //some code
    $str =  eval(''.$array.$path.$key.';');
    $str = $value;
 }

set_val($_SESSION['basket'], $path, 'price', '30'); will set the price for CD-ROM to 30.

Is there a better way for doing this?

Thank you.

Answer 1

Here you go a code I have finetuned some time ago:

  function get_val($array,$path) {
    for($i=$array; $key=array_shift($path); $i=$i[$key]) {
      if(!isset($i[$key])) return null;
    }
    return $i;
  }

  function set_val(&$array,$path,$val) {
    for($i=&$array; $key=array_shift($path); $i=&$i[$key]) {
      if(!isset($i[$key])) $i[$key] = array();
    }
    $i = $val;
  }

See this test example, I believe it is what you are looking for:

  $data = array("x"=>array("y"=>array("z"=>"foo")));
  echo get_val($data,array("x","y","z")); // foo
  set_val($data,array("x","y","u"),"bar"); // $data["x"]["y"]["u"] = "bar";