php split array on change of value in column data

Question

I am trying to split array data into multiple arrays based on change in data value at known position (column).

$input =  array(
  array(1,2,3),
  array(4,5,3),
  array(7,8,4),
  array(9,10,4),
  array(11,12,4)
);

Here column 3 changes values from 3 to 4 and expected result is to have 2 arrays

$out1 = array(array(1,2,3),array(4,5,3));
$out2 = array(array(7,8,4), array(9,10,4), array(11,12,4));

since number of rows are variable, cannot use array_chunk since column 3 values are variable, cannot use array_filter number of output arrays are also variable. trying splice but failing...

Possible duplicate of PHP splitting array into two arrays based on value — Hearner
– Hearner, Commented Aug 1, 2019 at 7:33

splash58 · Accepted Answer · 2019-08-01 07:49:57Z

2

You can use array_reduce to make new array, where index will be equal to last numbers in items

$new = array_reduce($input, function($c, $x) {  $c[$x[2]][] = $x; return $c; }, [] );
$out1 = $new[3];
$out2 = $new[4];

demo

But if array is not sorted and you want to split at points of changing that number, the code can be

$i = -1;
$last = null;
$new = [];
foreach($input as $x) {
    if ($x[2] != $last) {
        $i++;
        $last = $x[2];
    }
    $new[$i][] = $x;
}

demo

edited Aug 1, 2019 at 7:49

answered Aug 1, 2019 at 7:37

splash58

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5 Comments

prac Over a year ago

Yes this works for the regular array as in the question. but not for an array with key=>values like $a = array( array('k1'=>1,'k2'=>2,'k3'=>3), array('k1'=>4,'k2'=>5,'k3'=>3), array('k1'=>7,'k2'=>8,'k3'=>4), array('k1'=>9,'k2'=>10,'k3'=>4) ); where i get Undefined offset: 2 could you clarify

splash58 Over a year ago

Change $x2 with end($x)

prac Over a year ago

{ $c[end($x)] = $x; return $c; } outputs only the last arrays of each set. demo at . sandbox.onlinephpfunctions.com/code/…

splash58 Over a year ago

You should add empty square brackets as in my code (i can't write it on this phone :))

splash58 Over a year ago

sandbox.onlinephpfunctions.com/code/…

Rahul · Accepted Answer · 2019-08-01 07:37:11Z

You can use split index with index of array,

$out1 = $out2 = [];
$splitIndex = 2;
foreach($input as $k => $v){
    if($k < $splitIndex){
        $out1[] = $v;
    }else{
        $out2[] = $v;
    }
}
print_r($out1);
print_r($out2);

Working demo

Output:-

Array
(
    [0] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
        )

    [1] => Array
        (
            [0] => 4
            [1] => 5
            [2] => 3
        )

)
Array
(
    [0] => Array
        (
            [0] => 7
            [1] => 8
            [2] => 4
        )

    [1] => Array
        (
            [0] => 9
            [1] => 10
            [2] => 4
        )

    [2] => Array
        (
            [0] => 11
            [1] => 12
            [2] => 4
        )

)

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