PHP - fast way to get previous array elements before specific key

Question

How can I get all previous element before a specific array key.

Here is my array:

$key = 256;

$array = (
125 => array(571, 570), 
284 => array(567, 566),
256 => array(562, 560),
110 => array(565, 563),
);

Now I want result like this:

$array = (
125 => array(571, 570), 
284 => array(567, 566)
);

possible duplicate here https://stackoverflow.com/questions/41713639/how-to-get-next-key-in-an-array-from-given-key-in-php — スージン, Nov 27 '17 at 02:05
@MDAbubakar Please rephrase your question, do you mean the elements *before* a given key? Because that's the results you are wanting. — Spencer Wieczorek, Nov 27 '17 at 02:12
Where is the attempt to self-solve? It didn't make its way into the posted question. — mickmackusa, Nov 27 '17 at 06:21
Is `$key` guaranteed to exist in the array? This is a necessary question for any method using `array_search ()`. — mickmackusa, Nov 27 '17 at 06:25
Possible duplicate of [PHP: How to delete all array elements after an index](https://stackoverflow.com/questions/21851127/php-how-to-delete-all-array-elements-after-an-index) — mickmackusa, Nov 27 '17 at 11:44

score 3 · Accepted Answer · answered Nov 27 '17 at 02:30

You can iterate through and push values to a newArray until you hit the key you are searching for:

$Key = 256;

$array = array(
"125" => array(571, 570), 
"284" => array(567, 566),
"256" => array(562, 560),
"110" => array(565, 563),
);

$newArray = [];

foreach($array as $key => $value) 
{   
  if($key == $Key) break;
  $newArray[$key] = $value;
}

print_r ($newArray); 
/*
=> Array ( 
    [125] => Array ( [0] => 571 [1] => 570 ) 
    [284] => Array ( [0] => 567 [1] => 566 ) 
   )
*/

Goma · Answer 2 · 2017-11-27T02:43:22.713

2

Get the numeric index of key first using array_search() and array_keys(). Then slice the array from the beginning to key's index using array_slice()

$index = array_search($key, array_keys($array)); // Get the numeric index of search key
$result = array_slice($array, 0, $index, true);  // Slice from 0 up to index

print_r($result); // Print result

edited Nov 27 '17 at 02:43

answered Nov 27 '17 at 02:34

Goma

2,018
1
10
19

ArtisticPhoenix · Answer 3 · 2017-11-27T02:48:39.680

You can do this weird thing:

$key = 256;

$array = array(
    125 => array(571, 570), 
    284 => array(567, 566),
    256 => array(562, 560),
    110 => array(565, 563),
);

print_r(array_slice($array, array_search($key, array_keys($array)), null, true));

Outputs

Array
(
    [256] => Array
        (
            [0] => 562
            [1] => 560
        )

    [110] => Array
        (
            [0] => 565
            [1] => 563
        )

)

UPDATE

I realize now that I look again, I did it backwards. I call dyslexic moment... To do it the right way is like this

print_r(array_slice($array, 0, array_search($key, array_keys($array)),true));

score 0 · Answer 4 · answered Dec 25 '21 at 12:03

0

$position = array_search($key, array_keys($array));
$output = array_slice($array, 0, $position);
print_r($output);

DEMO: https://3v4l.org/nmnDv

answered Dec 25 '21 at 12:03

esqeudero

102
2
9

PHP - fast way to get previous array elements before specific key

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