How to map array depth?

Question

I'm not sure how to call this, and I can't find what I'm looking for because I must be looking for the wrong keywords, so even the right search term would help me out here:

I have a $map array and a $data array. The $data array is a dynamic array based on a xml that is parsed. Simplified Example:

$data = array('a' => array(0=> array('hello'=>'I want this data')));

$map = array('something' => 'a.0.hello');

Now I'd like to set $test to the value of $data['a']['0']['hello'] by somehow navigating there using $map['something']. The idea behind this is to create a mapping array so that no code changes are required if the xml format is to be changed, only the mapping array. Any help in the good direction is very much appreciated :)

are you searching for the value of something to navigate the I want this data — Murad Hasan
– Murad Hasan, Commented May 30, 2016 at 9:32
Can you be more specific on what exactly you need? Do you want something to point to a string? Maybe make a function which explodes the string and uses its elements as index(s) for the other array?! — JRsz
– JRsz, Commented May 30, 2016 at 9:34

splash58 · Accepted Answer · 2016-05-30 09:53:46Z

3

// Set pointer at top of the array 
$path = &$data;
// Asume that path is joined by points
foreach (explode('.', $map['something']) as $p) 
   // Make a next step
   $path = &$path[$p];
echo $path; // I want this data

edited May 30, 2016 at 9:53

answered May 30, 2016 at 9:34

splash58

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5 Comments

splash58 Over a year ago

that no code changes are required if the xml format is to be changed, only the mapping array - i understood it so

splash58 Over a year ago

@FrayneKonok Maybe, difficult to write such code :)

Murad Hasan Over a year ago

I think the OP want to create the map array from data array.

jwebdev Over a year ago

Splash had it right, turns out I was thinking way to complicated!

splash58 Over a year ago

Read there - php.net/manual/en/language.references.php and ask if you still have a question

Mulan · Accepted Answer · 2016-05-30 09:40:14Z

There's not really a good way to programmatically access nested keys in arrays in PHP (or any other language I can think of, actually).

function getDeepValue(&$arr, $keys) {
  if (count($keys) === 0)
    return $arr;
  else
    return getDeepValue($arr[$keys[0]], array_slice($keys, 1));
}

$data = ['a' => [0=> ['hello'=>'I want this data']]];
$map = ['something' => getDeepValue($data, ['a', '0', 'hello'])];

var_dump($map);

// array(1) {
//   ["something"]=>
//   string(16) "I want this data"
// }

If you want to use the string of keys, just use

getDeepValue($arr, explode('.', 'a.0.hello'))

If that's a common operation you have to do, you could add another layer of abstraction that accepts string-based lookup of deep values.

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