PHP - split array by key

Question

I've got the following array, containing ordered but non consecutive numerical keys:

Array
(
    [4] => 2
    [5] => 3
    [6] => 1
    [7] => 2
    [8] => 1
    [9] => 1
    [10] => 1
)

I need to split the array into 2 arrays, the first array containing the keys below 5, and the other array consisting of the keys 5 and above. Please note that the keys may vary (e.g. 1,3,5,10), therefore I cannot use array_slice since I don't know the offset.

Do you know any simple function to accomplish this, without the need of using a foreach ?

You should really specify if you need to keep the original keys or not. — Sergiu Paraschiv
– Sergiu Paraschiv, Commented Jun 27, 2014 at 11:45

Sergiu Paraschiv · Accepted Answer · 2014-06-27 11:49:59Z

3

Just found out array_slice has a preserve_keys parameter.

$a = [
    4 => 2,
    5 => 3,
    6 => 1,
    7 => 2,
    8 => 1,
    9 => 1,
    10 => 1
];

$desired_slice_key = 5;
$slice_position = array_search($desired_slice_key, array_keys($a));

$a1 = array_slice($a, 0, $slice_position, true);
$a2 = array_slice($a, $slice_position, count($a), true);

edited Jun 27, 2014 at 11:49

answered Jun 27, 2014 at 11:32

Sergiu Paraschiv

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5 Comments

Barmar Over a year ago

This seems like it would be more complex than foreach. Can you show the simple solution you're describing?

Sergiu Paraschiv Over a year ago

Yeah, you're right. Just wrote the code and it's far from simple.

Sergiu Paraschiv Over a year ago

But it's pretty short using the preserve_keys parameter added in 5.0.2

Barmar Over a year ago

Note that this answer assumes that the original array is sorted by the keys.

Sergiu Paraschiv Over a year ago

Yes it does. But specifically writing "5 and above" pretty much tells us they are.

Keir Lavelle · Accepted Answer · 2014-06-27 11:56:35Z

0

you could use array_walk, passing in the arrays you wish to add the keys to by reference using the use keyword - something along the lines of this should work:

$splitArray = [1 => 2, 3 => 1, 5 => 2, 7 => 1, 9 => 3, 10 => 1];

$lt5 = [];
$gt5 = [];

array_walk($splitArray, function(&$val, $key) use (&$lt5, &$gt5) {
    $key < 5 ? $lt5[] = $key : $gt5[] = $key;
});

var_dump($lt5, $gt5);

answered Jun 27, 2014 at 11:56

Keir Lavelle

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