$U = $S = 100000;
$dimMax = 5;
for($u = 0;  $u < $U;  $u++ ) {   
  $minDistance  = 100;
  $group[$u]    = -99;
  for($s = 0;  $s < $S;  $s++ ) {
    $distance[$u][$s] = 0;
    for($dim = 0;  $dim < $dimMax;  $dim++ ) {
      $distance[$u][$s] = $distance[$u][$s] + ($input_train[$dim][$u] - $weight[$dim][$s])**2;
    }
    $distance[$u][$s] = sqrt($distance[$u][$s]) / $dimMax;
    if($distance[$u][$s] < $minDistance) {
      $minDistance = $distance[$u][$s];
      $minS = $s;
    }
  }
  $group[$u] = $minS;  
}