PHP - Make an associative array unique, key -> value and value -> key

Question

I have a little problem in php, which i find hard to explain in words. I have an associative array which contains key-value. I would like to make a function (or if there is already one) which would take an array as input and remove the duplicates but both ways.

For example:

In my array I have {a -> b} {a -> c} {b -> a} {b -> c} ...

From this view it does not seem like there is any duplicate, but to me {a -> b} and {b -> a} are duplicate. So I would like the function to see it as a duplicate and only return one of them.

I tried to use array_flip / array_unique to exchange the key and the values, in a loop but didn't quite work.

Could you help to find a way to do this even if it is array with a large length? or if there is a php function which does it.

Help would be really appreciated, thanks.

There is code to illustrate the idea:

For an array which would be like that:

Array ( 
    [0] => Array ( [0] => a [1] => b)
    [1] => Array ( [0] => a [1] => c )
    [2] => Array ( [0] => b [1] => a )
    [3] => Array ( [0] => b [1] => c )
)

So you only want to remove pairs that are identical, i.e. `a->b` & `b->a`, but not `a->b` & `a->c` or `a->b` & `c->b`? — Alasdair, Feb 23 '13 at 11:39
*{a -> b} {a -> c}* do you have multiple keys with the same name (not possible)..? If I understood correctly if key *a* also exists as a value for example *b => a* it's a duplicate for you? If not then [array_diff_assoc()](http://www.php.net/manual/en/function.array-diff-assoc.php) is probably the function you're looking for.. — kjetilh, Feb 23 '13 at 11:42
`[0] => Array ( [0] => a [1] => b)` this is not an associative array, either your question is misleading or your example is wrong. I guess its the former, because you are talking about duplicate keys, which would not be possible. — Fabian Schmengler, Feb 23 '13 at 12:57
the reason why it like that is because i want to be able to repeat the same key different times in the array. so to be able to have 'a' as key different times otherwise it wouldn't work I think because array keys are unique — StringerB, Feb 23 '13 at 13:11
or if you have a way of repeating the same key different time in the array, that would make it easier for me to also demonstrate — StringerB, Feb 23 '13 at 13:13

Antonio Papa · Answer 1 · 2013-02-23T12:00:05.437

4

This will remove your dublicates

foreach($array as $key => $value){
     if (isset($array[$key])){
        if(isset($array[$value])){
            if($array[$value] == $key){
                unset($array[$value]);
            }
        }
     }
 }

edited Feb 23 '13 at 12:00

answered Feb 23 '13 at 11:38

Antonio Papa

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With the array ` 'b', 'b' => 'a', 'c' => 'd', 'd' => 'c' ); ?>` the array returns empty – kjetilh Feb 23 '13 at 11:55
1

It returns Array ( [a] => b [c] => d ) – Antonio Papa Feb 23 '13 at 12:02
I didn't ask the question, @StringerB did, I encourage him to mark your answer as well – kjetilh Feb 23 '13 at 12:06
thanks for your replies, to be honest I don't understand your code! – StringerB Feb 23 '13 at 12:26
$array is your array with dublicate values if you do the foreach it will remove all the dublicates exaple if your array is $array = array( 'a' => 'b', 'b' => 'a', 'c' => 'd', 'd' => 'c' ); the result is Array ( [a] => b [c] => d ) – Antonio Papa Feb 23 '13 at 13:51

score 2 · Answer 2 · answered Feb 23 '13 at 13:03

This should work:

function cleanArray($array)
{
   $newArray = array();
   foreach ($array as $key => $val) {
      if (isset($array[$val]) && $array[$val] == $key) {
         if (!isset($newArray[$key]) && !isset($newArray[$val])) {
            $newArray[$key] = $val; 
         }      
         unset($array[$key], $array[$val]);
      }
   }    
   return array_merge($array, $newArray);
}

Working example here.

PHP - Make an associative array unique, key -> value and value -> key

2 Answers2

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