php - 函数而不是数字，有时返回 Null

Question

嗨，我有以下代码：

function GetID($d1, $d2, $d3, $d4) {
   if ($d1 == '3') {
      if ($d2 == '3') {
         if ($d3 == 1) {
            $randval = mt_rand(1,100);
            if ($randval >= 1 && $randval <= 33) $weathern = 1;
            if ($randval >= 34 && $randval <= 66) $weathern = 3;
            if ($randval >= 67 && $randval >= 100) $weathern = 2;
         }
         elseif ($d3 == 2) {
            $randval = mt_rand(1,100);
            if ($randval >= 1 && $randval <= 45) $weathern = 1;
            if ($randval >= 46 && $randval <= 70) $weathern = 2;
            if ($randval >= 71 && $randval <= 100) $weathern = 3;
         }
         elseif ($d3 == 3) {
            $randval = mt_rand(1,100);
            if ($randval >= 1 && $randval <= 10) $weathern = 1;
            if ($randval >= 11 && $randval <= 35) $weathern = 2;
            if ($randval >= 36 && $randval <= 55) $weathern = 3;
            if ($randval >= 56 && $randval <= 85) $weathern = 5;
            if ($randval >= 86 && $randval <= 100) $weathern = 6;
         }
         elseif ($d3 == 5) {
            $randval = mt_rand(1,100);
            if ($randval >= 1 && $randval <= 30) $weathern = 3;
            if ($randval >= 31 && $randval <= 45) $weathern = 4;
            if ($randval >= 46 && $randval <= 75) $weathern = 6;
            if ($randval >= 76 && $randval <= 100) $weathern = 7;
         }
         elseif ($d3 == 6) {
            $randval = mt_rand(1,100);
            if ($randval >= 1 && $randval <= 30) $weathern = 5;
            if ($randval >= 31 && $randval <= 60) $weathern = 7;
            if ($randval >= 61 && $randval <= 75) $weathern = 2;
            if ($randval >= 76 && $randval <= 100) $weathern = 3;
         }
         elseif ($d3 == 7) {
            $randval = mt_rand(1,100);
            if ($randval >= 1 && $randval <= 35) $weathern = 8;
            if ($randval >= 36 && $randval <= 60) $weathern = 5;
            if ($randval >= 61 && $randval <= 85) $weathern = 2;
            if ($randval >= 86 && $randval <= 100) $weathern = 3;
         }
         elseif ($d3 == 8) {
            $randval = mt_rand(1,100);
            if ($randval >= 1 && $randval <= 35) $weathern = 3;
            if ($randval >= 36 && $randval <= 60) $weathern = 2;
            if ($randval >= 61 && $randval <= 85) $weathern = 1;
            if ($randval >= 86 && $randval <= 100) $weathern = 5;
         }
      }
   }
   return $weathern;
}

当我调用这个函数时：

echo GetID(3, 3, 1, 1);

它按预期工作（我得到数字），但有时它什么也不返回。

任何想法为什么会发生这种情况？

我是 PHP 新手，但我在这里看不到任何问题

Answer 1

$randval >= 67 && $randval >= 100

错了，用

$randval >= 67 && $randval <= 100

反而。