code: public function get($int_i, $int_j)
      {
          if (!is_integer($int_i) || !is_integer($int_j)) {
              throw new \InvalidArgumentException('Indices must be integers.');
          }
  
          if(
              $int_i >= $this->size->rows
              ||
              $int_j >= $this->size->cols
              ||
              $int_i < 0
              ||
              $int_j < 0
          )
          {
              throw new \InvalidArgumentException('Row’s index or column’s index does not exist!');
          }
  
          return $this->arr[$int_i][$int_j];
      }
docs: Gets one item at given row and column.
  
  @throw \InvalidArgumentException If indexes are not integers
  @throw \InvalidArgumentException If one of the given indexes does not exist.
  @param  integer $int_i Row index
  @param  integer $int_j Column index
  @access public
  @return float