Stockholm Syndrome

var arr1 = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]];
var arr2 = [[10, 20, 30, 40], [50, 60, 70, 80], [90, 100, 110, 120]];
var arr3 = [[100, 200, 300, 400], [500, 600, 700, 800], [900, 1000, 1100, 1200]];

function summ_array(...arrs){
   return arrs.reduce((acc,arr)=>{
      if( Array.isArray(arr))
         arr.forEach((subarr, i)=>{
            if(!Array.isArray(acc[i])) 
               acc[i] = []
            if( Array.isArray(subarr))
               subarr.forEach((v, j)=>{
                  if(!acc[i][j]) 
                     acc[i][j] = 0;
                  acc[i][j]+=v;
               });   
         });
      return acc;
   },[]);
}
var summ = summ_array(arr1, arr2, arr3);
console.log(summ);

<?php
$arr = [100,125,75,175,25,300,275,325,375];
$step = 50;

$b = []; //-1 - deny, 0 - not set, 1 - has interval
$int = []; //intervals if necessary 
$step2 = intdiv($step,2);
$arr = array_values(array_filter($arr, function($v) use ($step2,&$b,&$int) {
    $i = intdiv($v,$step2);
    $mod = $v % $step2;
    $res = true;
    if (isset($b[$i])) {
        if ($b[$i] === -1) $res = false;
        elseif ($mod < $int[$i][0] or $mod > $int[$i][1]) $res = false;
    }
    $b[$i] = -1;
    $b[$i+1] = -1;
    $b[$i-1] = -1;
    if (!isset($b[$i+2])) {
        $b[$i+2] = 1;
        $int[$i+2] = [$mod,$step2];
    } elseif ($b[$i+2] === 1) {
        if ($int[$i+2][0] < $mod) {
            $int[$i+2][0] = $mod;
            if ($int[$i+2][0] >= $int[$i+2][1]) $b[$i+2] = -1;
        }
    }
    if (!isset($b[$i-2])) {
        $b[$i-2] = 1;
        $int[$i-2] = [0,$mod];
    } elseif ($b[$i-2] === 1) {
        if ($int[$i-2][1] > $mod) {
            $int[$i-2][1] = $mod;
            if ($int[$i-2][0] >= $int[$i-2][1]) $b[$i-2] = -1;
        }
    }
    return $res;
}));

var_dump($arr); // [100, 175, 25, 300, 375]
?>