two-dimensional factorial (sorta) function

//--------------------------------------------------------------------
/**
 * recursive function that takes in a 2d array and returns 1d array containing all possible
 * column-row combinations.
 * 
 * @param a    - 2d array
 * @param col  - column value to work with.  original function call should have this at 0
 * @param row  - row value to work with.  oringinal function call should have this at 0
 * @param tempSentence  - temp sentence that contains sentence fragments before they are finished and 
 *                      - entered into $sentence
 * @returns    1d array
 * 
 * example call: $returnArray = doBuilding($wordArray);
 * example use: array--
 *                this function works
 *                ths  fnctn    wrks
 *                thz  fctn     wrx
 *                thiz          wks
 *
 *              returns-- 
 *                thisfunctionworks
 *                thisfunctionwrks
 *                thisfunctionwrx
 *                thisfunctionwks
 *                thisfnctnworks
 *                thisfnctnwrks
 *                etc...
 */
   function doBuilding($a,$col=0,$row=0,$tempSentence="")
   {  //if there are more columns to the right, add this column to temp sentence and move on to
      //next column
      if ($col+1 < count($a))
      {  //for each row in this column, add data to temp array and call function with next right row
         for ($i=0; $i < count($a[$col]); $i++)
         {  $temp = $tempSentence . $a[$col][$i];
            $temp2 = $this->doBuilding($a,$col+1,$i,$temp);
            $sentence = array_merge($sentence,$temp2); 
         }

      //else add all rows from this column to end of temp sentence and return array
      }else
      {  for ($i=0; $i < count($a[$col]); $i++)
            $tempArray[$i] = $tempSentence . $a[$col][$i];
         return $tempArray;
      }

      return $sentence;
   }