PHP sort/reorder the array by specific start on key

Question

I want to sort or reorder the array element based on start on value.

My array:

[
    0 => 'Sun',
    1 => 'Mon',
    2 => 'Tue',
    3 => 'Wed',
    4 => 'Thu',
    5 => 'Fri',
    6 => 'Sat'
]

$startOn = 3;

Expected Output :

[
    3 => 'Wed',
    4 => 'Thu',
    5 => 'Fri',
    6 => 'Sat',
    0 => 'Sun',
    1 => 'Mon',
    2 => 'Tue',
]

I tried using uksort but it does not return the expected output.

uksort($weekDays, function ($a, $b) use ($startOn) {
    return $startOn-$a;
});

Current output :

[
    3 => 'Wed'
    4 => 'Thu'
    5 => 'Fri'
    6 => 'Sat'
    2 => 'Tue'
    1 => 'Mon'
    0 => 'Sun'
]

That's not sorting. Just slice subarray and append it to the end. — u_mulder
– u_mulder, Commented Sep 17, 2019 at 5:33
You can use ($k + 7 - $startOn) % 7 as the key in uksort, check my answer — LF-DevJourney
– LF-DevJourney, Commented Sep 17, 2019 at 6:13

Rakesh Jakhar · Accepted Answer · 2019-09-17 05:52:08Z

1

You can use foreach

$start = 3;
$r1 = $r2 = [];
foreach($a as $k => $v){
  ($k >= $start) ? ($r1[$k]=$v) : ($r2[$k]=$v);
}
$r = $r1 + $r2;
print_r($r);

Working example :- https://3v4l.org/1KDoR

edited Sep 17, 2019 at 5:52

answered Sep 17, 2019 at 5:33

Rakesh Jakhar

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1 Comment

Hiren Bhut Over a year ago

Method 1 - It's ok but when $startOn = 0 that error and Method 2 - when $startOn = 0 that time remove the last element

Nigel Ren · Accepted Answer · 2019-09-17 06:00:03Z

1

As the array_slice() code has been removed from the other answer, thought I would add my version here.

The main thing is to set the fourth parameter to true so that it retains the key...

$weekDays = array_slice($weekDays, $startOn, null, true) 
        + array_slice($weekDays, 0, $startOn, true);

answered Sep 17, 2019 at 6:00

Nigel Ren

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Comments

LF-DevJourney · Accepted Answer · 2019-09-17 06:11:22Z

1

With uksort, check the Demo

$startOn = 3;
uksort($array,function($a,$b)use($startOn){return ($a + 7 - $startOn) % 7 - ($b + 7 - $startOn) % 7;});
print_r($array);

answered Sep 17, 2019 at 6:11

LF-DevJourney

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Comments

Rahul · Accepted Answer · 2019-09-17 07:51:11Z

1

Here is working solution,

$k = array_search(3, array_keys($arr));
$arr = array_slice($arr,$k,null,true) + array_slice($arr,0,$k,true);
print_r($arr);

Demo.

Output:-

Array
(
    [3] => Wed
    [4] => Thu
    [5] => Fri
    [6] => Sat
    [0] => Sun
    [1] => Mon
    [2] => Tue
)

array_search — Searches the array for a given value and returns the first corresponding key if successful

array_slice — Extract a slice of the array

Note:

array_slice() will reorder and reset the integer array indices by default. This behaviour can be changed by setting preserve_keys to TRUE. String keys are always preserved, regardless of this parameter.

answered Sep 17, 2019 at 7:51

Rahul

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