# Shift one value of array values to the beginning

Given an integer $value in the range of 1, 2, 3, I want to get an array that starts with$value and proceeds with the remaining two integers from above in arbitrary order. The best I could think of was doing something like this:

switch ($value) { case '1':$array = [1,2,3];
break;

case '2':
$array = [2,1,3]; break; case '3':$array = [3,1,2];
break;
}

Is there a shorter and more beautiful way of doing that? Something like that:

$array = push_to_top_of_array($value,[1,2,3]);
• I should have asked earlier... how is $array used after this code? would there ever be a case where other values would exist in that array? – Sᴀᴍ Onᴇᴌᴀ May 31 '18 at 15:00 • @SamOnela the array goes through a foreach loop. There is no case where other values would exist. – Adam May 31 '18 at 15:49 • Okay- what does the foreach loop do with it? Can you describe the output of the script? For code review, it is best to have a broad picture of what the code does. – Sᴀᴍ Onᴇᴌᴀ May 31 '18 at 15:50 ## 4 Answers Is there a shorter and more beautiful way of doing that? • shorter: yes • more beautiful: well, that sounds subjective... you can be the judge of the approaches below. One approach would be to take off the value using$index with array_splice() and then put it (the first element from that spliced array) at the beginning using array_unshift():

$array = [1, 2, 3]; array_unshift($array, array_splice($array,$value - 1, 1)[0]);

Another approach would be to merge the spliced array and the original array using array_merge():

$array = [1, 2, 3];$array = array_merge(array_splice($array,$value - 1, 1), $array); See it demonstrated in this playground example. Yes, for three array elements you can write:$arr = [
($value - 1) % 3 + 1, ($value + 0) % 3 + 1,
($value + 1) % 3 + 1 ]; The main ingredient here is the$value modulo 3 expression. The above code contains some redundancies, which I have kept to clearly show the construction of the code. If you absolutely need faster code instead of readable code, the above is equivalent to:

$arr = [$value,
$value % 3 + 1, 5 -$value - $value % 3 ]; Or, the brute force variant: // To be executed only once in the program.$arrs = [[], [1, 2, 3], [2, 3, 1], [3, 1, 2]];

// And then, whenever you need it:
$arr =$arrs[$value]; I hate hardcoded solutions and prefer generalized ones. You never know when your array will get a 4th element and break all the application. So a generalized solution would be like • get a key for the desired value • remove this element from array • add its value to the beginning of an array in PHP it would be like function push_to_top_of_array($value, $array) {$key = array_search($value,$array);
if ($key === false) { throw new \OutOfRangeException("Value not found"); } unset($array[$key]); array_unshift($array, $value); return$array;
}

$value = 2;$array = [3, 5, 2, 4];
$array = push_to_top_of_array($value, $array); I'm not sure if "more beautiful" means you want a one-liner, but here are two more concise ways to perform the task: *note, this doesn't validate the$value as being one of the element values -- if this is a necessary component of your project, then please clarify in your question.

Code: (Demo)

$value = 2;$array = [1, 2, 3];
array_unshift($array,$value);  // prepend a duplicate
var_export(array_unique($array)); // kill the original echo "\n---\n";$value = 2;
$array = [1, 2, 3]; var_export(array_unique(array_merge([$value],\$array)));  // prepend a duplicate, kill the original

Output:

array (
0 => 2,
1 => 1,
3 => 3,
)
---
array (
0 => 2,
1 => 1,
3 => 3,
)

On huge arrays, statistics have shown array_flip(array_flip()) out performs array_unique() but that would certainly be less beautiful and if you were dealing with big array I'm sure you would have mentioned that.