PHP - IF doing all the time only first condition, why?

why the IF(the lastest one with else if and else) is doing all the time only first condition and only the first part ($filtry_1value[$key] = 'min_cena'), even if the condition shouldnt be true. I have another solution (less dynamic), if I will not fix this one, but I would like to know, why it is not working... I think it will be a trivial thing, but I cannot see it.

PS: I am working with laravel.

$filtry_1value = ['stat', 'lokalita', 'patro', 'min_cena', 'max_cena', 'min_uzitna_plocha', 'max_uzitna_plocha'];

  foreach ($filtry_1value as $key => $filtr_1value) {
  $filtr_1value = \Request::has($filtr_1value) ? \Request::get($filtr_1value) : null;
    if(!empty($filtr_1value)){
      if ($filtry_1value[$key] = 'min_cena' OR $filtry_1value[$key] = 'min_uzitna_plocha') {
        $query->where(substr($filtry_1value[$key], 4),'>=',$filtr_1value);
      }
      elseif ($filtry_1value[$key] = 'max_cena' OR $filtry_1value[$key] = 'max_uzitna_plocha') {
        $query->where(substr($filtry_1value[$key], 4),'<=',$filtr_1value);
      }
      else {
        $query->where($filtry_1value[$key],'=', $filtr_1value);
      }
    }
  }