记录工作用过的php数组封装

function range($step = 10, $max = 100){
      if ($step < 1 || $step > $max){
          return [];
      }
      $array = [];
      for ($i = $step; $i <= $max; $i += $step){
          $array[$i] = $i;
      }
      return $array;
 }

function isAssoc(array $array){
      $keys = array_keys($array);
      return array_keys($keys) !== $keys;
 }