Question

How to group all differences between consecutive numbers from associative array? Below is the array which I’m using

need to group (2,3)(7,8) with they difference , ignore (11,6,5,9)

$array = array(
    2 =>"12",
    3 =>"12",
    11 => "16",
    6 => "15",
    5 => "14",
    7 => "16",
    8 => "17",
    9 => "18")

Below is the code which I’m using to group the array, but it’s not working:

foreach ($array as $k => $v) {
    echo  $prev;
    if (isset($prev)) {
        if (($v - $prev) != 1) $newArray[] = $v;
    } else { $newArray[] = $v; }
    $prev = $v;
}
echo '<pre>';
print_r($newArray);

Currently I’m getting this:

Array
(
    [0] => 12
    [1] => 12
    [2] => 16
    [3] => 15   
    [4] => 16
)

but I need the O/P to be (2,3)=0 difference, (7,8)=1 difference, i. e.

array(
    [0]=>0,
    [1]=>1
);

Answer 1

So here you go.

$newArray = array();
foreach ($array as $k => $v) {
    if (isset($prev) && $k == $prev + 1) {
        $newArray[] = $v - $array[$prev];
    }
    $prev = $k;
}

This produces the array for three consecutive pairs:

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

If you want to stop after two pairs, add a running counter $i = 0; before the foreach and exit with if (++$i >= 2) break; inside the if in the loop:

$newArray = array();
$i = 0;
foreach ($array as $k => $v) {
    if (isset($prev) && $k == $prev + 1) {
        $newArray[] = $v - $array[$prev];
        if (++$i >= 2) break;
    }
    $prev = $k;
}