Intersect and Sort an Array by keys based on another Array?

Question

Similar to the question: Sort an Array by keys based on another Array? only I want to drop any keys that arent in common.

Essentially I tried filtering the variables by the keys via array_intersect_key($VARIABLES, array_flip($signature_args)); and then tried to sort it with array_merge(array_flip($signature_args), $filtered)

Shown here:

$VARIABLES = array('3'=>'4', '4'=>'5', '1'=>'2');
$signature_args = array('1', '2', '3');

$filtered = array_intersect_key($VARIABLES, array_flip($signature_args));
var_dump($filtered);

var_dump(array_merge(array_flip($signature_args), $filtered));

produces:

array(2) {
  [3]=>
  string(1) "4"
  [1]=>
  string(1) "2"
}
array(5) {
  [0]=>
  int(0)
  [1]=>
  int(1)
  [2]=>
  int(2)
  [3]=>
  string(1) "4"
  [4]=>
  string(1) "2"
}

and not the

array(2) {
  [3]=>
  string(1) "4"
  [1]=>
  string(1) "2"
}
array(2) {
  [1]=>
  string(1) "2"
  [3]=>
  string(1) "4"
}

that I expected, why?

Before your var_dump do: `ksort($filtered);` does that do the trick for you? — Rizier123, Jan 06 '15 at 00:39
@Rizier123 No, it doesnt fix the problem. If you mean to replace the `var_dump(array_merge(array_flip($signature_args), $filtered));` with `ksort($filtered);` that only works if `$signature_args` is sorted — chacham15, Jan 06 '15 at 00:42
Works fine for me even if `$signature_args` isn't sorted?! See: http://ideone.com/u3CGjG — Rizier123, Jan 06 '15 at 00:44
@Rizier123 http://ideone.com/7i6FvH see, its in the wrong order (the result is supposed to be in the same order as the keys of `$signature_args`) — chacham15, Jan 06 '15 at 00:46
@Rizier123 yeah, in your example the keys are '2', '3', '1', so the result so be in the same order: '3', '1' — chacham15, Jan 06 '15 at 00:51
@Rizier123 correct, that is the intended purpose of the second statement: `array_merge(array_flip($signature_args), $filtered)` — chacham15, Jan 06 '15 at 00:54

score 1 · Accepted Answer · edited Jan 06 '15 at 01:27

1

This should work for you:

<?php

    $VARIABLES = array('3'=>'4', '4'=>'5', '1'=>'2');
    $signature_args = array('2', '3', '1');

    $filtered = array_intersect_key($VARIABLES, array_flip($signature_args));
    var_dump($filtered);

    $ordered = array();
    foreach ($signature_args as $key) {
        if(!empty($filtered[$key]))
        $ordered[$key] = $filtered[$key] ;
    }

    var_dump($ordered);

?>

Or if you want you can use this:

array_walk($signature_args, function($key) { 
    if(!empty($filtered[$key])) $ordered[$key] = $filtered[$key] ;
}, $ordered);

edited Jan 06 '15 at 01:27

chacham15

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answered Jan 06 '15 at 01:22

Rizier123

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hmm, I just did a small fix, but if we're going to use our own loop, to create the result array, then theres no point in generating the `$filtered` variable, we can take the value directly from `$VARIABLES`. i.e. `$ordered[$key] = $VARIABLES[$key];` – chacham15 Jan 06 '15 at 01:29

score 0 · Answer 2 · answered May 06 '22 at 00:14

To use the "allowed" array not only to filter the input array but also to order the output, filter both arrays by each other, then replace (or merge) the input array into the allowed array.

Code: (Demo)

$input = ['3' => '4', '4' => '5', '1' => '2'];
$allowed = ['1', '2', '3'];

$flipAllowed = array_flip($allowed);

var_export(
    array_replace(
        array_intersect_key($flipAllowed, $input), // filtered allowed
        array_intersect_key($input, $flipAllowed) // filtered input
    )
);

Output:

array (
  1 => '2',
  3 => '4',
)

Intersect and Sort an Array by keys based on another Array?

2 Answers2