Split an array into multiple arrays depending on number of similar adjacent values

Question

So I have an array containing multiple values like this

$input_array = array('45', '21', '45', '45', '45', '29', '35', '35', '21');

Now I want to split it into multiple arrays to group adjacent values if they are similar. For Example, the above array should split into 6 different arrays

$input_array_1 = array('45');

$input_array_2 = array('21');

$input_array_3 = array('45', '45', '45');

$input_array_4 = array('29');

$input_array_5 = array('35', '35');

$input_array_6 = array('21');

is this something possible in PHP?

is this something possible in PHP? - fortunately yes it is. Have you tried anything yourself yet? — Nigel Ren
– Nigel Ren, Commented Aug 12, 2019 at 18:41
Yes, I tried using array_chunk() function but I have no idea how can I dynamically change its 'size' parameter and run the function again every time. I googled for an answer but did not find anything which can help me solve this issue — T.Prasad
– T.Prasad, Commented Aug 12, 2019 at 18:47
write the code you tried to solve your problem and we can help you — Giacomo M
– Giacomo M, Commented Aug 12, 2019 at 19:09
@waterloomatt That doesn't handle the adjacent aspect of this problem, does it? I mean, wouldn't it group all the 45s together in the above example? — Don't Panic
– Don't Panic, Commented Aug 12, 2019 at 19:17

Caconde · Accepted Answer · 2019-08-13 02:36:55Z

I don't recommend the use of dynamic number of resulting vars like you asked in your question. It's better to have the result inside an array. This way you can cycle through the array indexes, instead of guessing how many $input_array_(number) your code generated.

$input_array = array('45', '21', '45', '45', '45', '29', '35', '35', '21');

$result = [];
$index = 0;
$processedElement = null;
foreach ($input_array as $currentElement) { 
    if ($processedElement != $currentElement) {
        $index++;   
    }
    $result[$index][] = $currentElement;
    $processedElement = $currentElement;
}

Printing $result will give you:

Array
(
    [0] => Array
        (
            [0] => 45
        )
    [1] => Array
        (
            [0] => 21
        )
    [2] => Array
        (
            [0] => 45
            [1] => 45
            [2] => 45
        )
    [3] => Array
        (
            [0] => 29
        )
    [4] => Array
        (
            [0] => 35
            [1] => 35
        )
    [5] => Array
        (
            [0] => 21
        )
)

Lawrence Cherone · Accepted Answer · 2019-08-12 19:18:11Z

You can use a simple foreach to loop though, then check the last value in the new array and append, to get the global vars, create an array first then extract, as shown below.

<?php
$input_array = array('45', '21', '45', '45', '45', '29', '35', '35', '21');

$result = [];

foreach ($input_array as $key => $value) {
    // get last item in array
    $last = end($result);

    // does last == this one
    if (isset($last[0]) && $last[0] === $value) {
        // append it
        $result['input_array_'.count($result)][] = $value;
    } else {
        // create new
        $result['input_array_'.(count($result)+1)][] = $value;
    }
}

print_r($result);

// to conform to question (not required)
extract($result);
print_r($input_array_3);

Result:

Array
(
    [input_array_1] => Array
        (
            [0] => 45
        )

    [input_array_2] => Array
        (
            [0] => 21
        )

    [input_array_3] => Array
        (
            [0] => 45
            [1] => 45
            [2] => 45
        )

    [input_array_4] => Array
        (
            [0] => 29
        )

    [input_array_5] => Array
        (
            [0] => 35
            [1] => 35
        )

    [input_array_6] => Array
        (
            [0] => 21
        )

)

Array
(
    [0] => 45
    [1] => 45
    [2] => 45
)

https://3v4l.org/RHsY4

Ho Phat · Accepted Answer · 2019-08-12 19:20:36Z

0

You can try. Hope it helps you

$input_array = array('45', '21', '45', '45', '45', '29', '35', '35', '20');

$allChunk = [];
$Chunk = [];
echo "<pre>";
foreach ($input_array as $value) {
    $chunk[] = $value;
    if(in_array(next($input_array),$chunk)) {
        continue;
    }
    $allChunk[] = $chunk;
    unset($chunk);
}
var_dump($allChunk);

answered Aug 12, 2019 at 19:20

Ho Phat

11 bronze badge

Comments

Nigel Ren · Accepted Answer · 2019-08-12 19:21:22Z

This method builds up a list of similar values, then when the value changes it adds this list to the end of the output array. The only thing is the first time in it has an empty list, rather than exclude adding it, I use array_shift() to remove this blank entry at the end...

$input_array = array('45', '21', '45', '45', '45', '29', '35', '35', '21');
$output = [];
$temp = [];
foreach ( $input_array as $value )  {
    if ( $value != ($temp[0]??'') ){
        $output[] = $temp;
        $temp = [$value];
    }
    else    {
        $temp[] = $value;
    }
}
array_shift($output);
$output[] = $temp;
print_r($output);

gives the output (truncated)...

Array
(
    [0] => Array
        (
            [0] => 45
        )

    [1] => Array
        (
            [0] => 21
        )

    [2] => Array
        (
            [0] => 45
            [1] => 45
            [2] => 45
        )
...

Dhairya Lakhera · Accepted Answer · 2019-08-12 19:22:50Z

0

$input_array = array('45', '21', '45', '45', '45', '29', '35', '35', '21');

$arr=array();
$prev_value=null;
foreach ($input_array as $key => $value) {
    if($value==$prev_value){
       array_push($arr[count($arr)-1],$value); 
    }
    else{
        $prev_value=$value;
        array_push($arr,array($value));
    }
}

print_r($arr);

edited Aug 12, 2019 at 19:22

answered Aug 12, 2019 at 19:14

Dhairya Lakhera

4,8385 gold badges41 silver badges70 bronze badges

Comments

mickmackusa · Accepted Answer · 2024-10-06 21:50:30Z

0

As demonstrated at Group associative elements by keys with contiguous dates to create an array of associative arrays, you won't need to keep track of indexes in the result array if you push references into the result array representing each group. This way you only push repeating values into the references. Demo

$result = [];
$last = null;
foreach ($array as $v) {
    if ($last !== $v) {
        unset($ref);
        $result[] =& $ref;
    }
    $ref[] = $v;
    $last = $v;
}
var_export($result);

answered Oct 6, 2024 at 21:50

mickmackusa♦

49.3k13 gold badges98 silver badges165 bronze badges

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