如何获得具有相同值的所有数组键

Question

I try pretty much everything, read trough whole php.net and I can't seem to find a way how to get array of all keys that have the same value.

For example this is array:

Array
(
   [869] => 87
   [938] => 89
   [870] => 127
   [871] => 127
   [940] => 127
   [942] => 123
   [947] => 123
   [949] => 75
)

Array we want in my case is:

Array
(
    [1] => array
    (
        [1] => 870
        [2] => 871
        [3] => 940
    )
    [2] => array
    (
        [1] => 942
        [2] => 947
    )
)

Answer 1

Here is a function that will do what you want. Many not be the simplest it could be but it works:

<?php

$myArray = array(
   869 => 87,
   938 => 89,
   870 => 127,
   871 => 127,
   940 => 127,
   942 => 123,
   947 => 123,
   949 => 75
);
$newArray = $foundKeys = array();
$itt = 0;
foreach($myArray as $i => $x){
    foreach($myArray as $j => $y ){
        if($i != $j && !in_array($i,$foundKeys) && $x == $y){
           if(!is_array($newArray[$itt])){
               $newArray[$itt] = array($i);
           }
           array_push($newArray[$itt],$j);
           array_push($foundKeys,$j);
        }
    }
    $itt++;
}
print_r($newArray);

results in:

Array
(
    [2] => Array
        (
            [0] => 870
            [1] => 871
            [2] => 940
        )

    [5] => Array
        (
            [0] => 942
            [1] => 947
        )

)