1 
     ";14             return;15         }16 17         if ($sum < $n) {18             combination($sum, $sum, $comb); #sum < n，则不可能需要比sum大的数来构成组合19             return;20         }21         22         #结果求得23         if ($sum == 0) {24             #输出元素组合25             echo "Combination: ";26             foreach ($comb as $val) {27                 echo $val . " ";28             }29             echo "
";30             return;31         }32 33         #组合里包含n的情况34         $comb[] = $n;35         combination($sum - $n, $n - 1, $comb);36 37         #组合里不包含n的情况38         array_pop($comb);39         combination($sum, $n - 1, $comb);40     }41 42     combination(10, 15, array());43 ?>