<div class="form-group">
   <label for="rule">过期规则：</label>
   <select name="rule" id="rule" class="form-control" style="width:20%; margin-right: 40px;">
    <option value="0" rule_id="0">请选择规则</option>
    @foreach($rules as $rule)
       <option value="{{ $rule->value }}" rule_id="{{ $rule->id }}">{{ $rule->name }}</option>
    @endforeach
   </select>
   <label for="time">过期倍数：</label>
   <select name="time" id="time" class="form-control" style="width:20%;">
     <option value="0">请选择倍数</option>
   </select>
   <span id="auto"></span>
</div>

$projects = Project::all();
$rules = Rule::all();
return view('key.create', compact('projects', 'rules'));

$("#rule").change(function() {
  $.post("{{ url('key/createTime') }}/"+$(this).find("option:selected").attr("rule_id"), {
    "_token": "{{ csrf_token() }}"
  }, function(data) {
    $("#time").html("<option value='0' name='time'>请选择倍数</option>");
    if(data.value == 0) { // 当选择请选择规则时，不会向下执行
      return false;
    }
    $.each(data, function(i, time) {
      $("#time").append("<option value='" + time.value + "'>" + time.value + "</option>");
    });
    $("#time").append("<option id='auto_time'>自定义</option>");
  });
});

public function createTime($rule_id)
{  // 当选中的为请选择规则时，自己拼一个数据，当success时，判断
 if ($rule_id == 0) {
   return ['id'=>0, 'value'=>0, 'rule_id'=>0];
 }
 $times = Rule::find($rule_id)->time;
 return $times;
}

public function time()
{
    return $this->hasMany(\App\Model\Time::class, 'rule_id', 'id');
}