Build associative array based on values of another associative array

问题

I'm looking for an elegant way to turn this array:

Array (
  [foo] => 1
  [bar] => 1
  [zim] => 3
  [dib] => 6
  [gir] => 1
  [gaz] => 3
)

Into this array:

Array (
  [1] => Array ( foo, bar, gir ),
  [3] => Array ( zim, gaz ),
  [6] => Array ( dib )
)

Note:, there is no relationship between the keys or values. They are completely arbitrary and used as examples only. The resulting array should be an associative array grouped by the values of the input array.

Thanks!

回答1:

$input = array(
  'foo' => 1,
  'bar' => 1,
  'zim' => 3,
  'dib' => 6,
  'gir' => 1,
  'gaz' => 3
)

$output = array();
foreach ( $input as $k => $v ) {
  if ( !isset($output[$v]) ) {
    $output[$v] = array();
  }

  $output[$v][] = $k;
}

回答2:

I think this will do it just fine:

foreach ($arr1 as $k => $val) $arr2[$val][] = $k;

where $arr1 is the original array outputting the new array to $arr2.

来源：https://stackoverflow.com/questions/2685516/build-associative-array-based-on-values-of-another-associative-array