PHP: find same keys in a multidimensional-array and merge the findings

Question

I have a multidimensional-array which looks like this:

$array = (
    [0] => array (
        ['WS'] => array(
             [id] => 2,
             [name] => 'hello'
             )
        )
    ), 
    [1] => array (
        ['SS'] => array(
             [id] => 1,
             [name] => 'hello2'
             )
        )
    ),
    [2] => array (
        ['WS'] => array(
             [id] => 5,
             [name] => 'helloAGAIN'
             )
        )
)

As you can see, $array[0] and $array[2] have the same key [WS]. I need a function to find those "same keys". Afterthat I would merge these two arrays into one. f.e.

$array =
(
    [0] => array 
        (
            ['WS'] => array
                (
                     [0] => array
                         (
                             [id] => 2,
                             [name] => 'hello'
                         ),
                     [1] => array
                         (
                            [id] => 5,
                            [name] => 'helloAGAIN'
                         )
                )
        ),
    [1] => array 
         (
             ['SS'] => array
                 (
                     [0] => array
                         (
                              [id] => 1,
                              [name] => 'hello2'
                         )
                 )
         )
    )

Hope you guys understand my problem. greets

Why not just iterate over it and rebuild your array? one pass and some kind of key lookup array should cover it. — JohnP
– JohnP, Commented Jan 12, 2012 at 17:51

DaveRandom · Accepted Answer · 2012-01-12 17:54:45Z

8

function group_by_key ($array) {
  $result = array();
  foreach ($array as $sub) {
    foreach ($sub as $k => $v) {
      $result[$k][] = $v;
    }
  }
  return $result;
}

See it working

answered Jan 12, 2012 at 17:54

DaveRandom

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1 Comment

Sv3n Over a year ago

Thank you. Its quite a good solution for me. Easy to understand and works well.

Robbo_UK · Accepted Answer · 2012-01-12 17:56:49Z

1

you can just loop through the array and delete matching elements

    $multiArray = array('0' => etc etc);
    $matches = array();

    foreach(multiArray as $key => $val)
    {
       $keyValToCheck = key($val);

       if(!in_array($keyValToCheck, $matches))
       {
          $matches[] = $keyValToCheck; // add value to array matches

          // remove item from array because match has been found
          unset($multiArray[$key][$keyValToCheck]);
       }
    }

answered Jan 12, 2012 at 17:56

Robbo_UK

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Comments

Cody O'Dell · Accepted Answer · 2012-01-12 18:05:09Z

1

You could simply eliminate the first level of your array and you would end up with something like this:

$array = (
    ['WS'] => array(
        [0] => array(
                [id] => 2,
                [name] => 'hello'
        ),
        [1] => array(
               [id] => 5,
               [name] => 'helloAGAIN'
        )
    ),
    ['SS'] => array(
        [0] => array(
              [id] => 1,
              [name] => 'hello2'
        )
    )
)

That way you can add things to your array like this:

$array['WS'][] = array();

answered Jan 12, 2012 at 18:05

Cody O'Dell

1916 bronze badges

1 Comment

Sv3n Over a year ago

thx a lot :) your structure of the array has led me to a solution of my problem. My thoughts about building a array was far to complicated.

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