Laravel页面刷新后保留下拉选择框选中值的问题

我原本的Blade下拉框代码：

<select id="Priority_id" style="width:180px;" class="myform-select">
    <option value="" selected>Select priority</option>
     @foreach ($priorities as $priority)
          <option value="{{ $priority->id }}">
              {{ $priority->Desc }}
          </option>
     @endforeach
</select>

为了保留表单提交后的旧选中值，我改成了这样：

<select id="Priority_id" style="width:180px;" class="myform-select">
    <option value="" selected>Select priority</option>
    @foreach ($priorities as $priority)
           <option value="{{ $priority->id }}" {{ ( old('Priority_id')==$priority->id ? "selected":"") }}>
                    {{ $priority->Desc }}
           </option>
    @endforeach
</select>

但页面刷新后，下拉框还是没法保留之前选中的值。

解决方法： #

• 给select添加name属性：old()函数依赖表单提交的字段名获取旧值，你的select只有id没有name，后端接收不到这个字段的值，自然没法通过old()回显。修改后：

  <select id="Priority_id" name="Priority_id" style="width:180px;" class="myform-select">
  

• 修正默认选项的selected逻辑：原来的默认选项硬写selected会覆盖old()的选中状态，应该改成只有无旧值时才选中默认选项：

  <option value="" {{ old('Priority_id') === null ? 'selected' : '' }}>Select priority</option>
  

• 确保类型匹配：如果old('Priority_id')是字符串、$priority->id是整数，直接用==可能出现隐式转换问题，建议统一类型后再比较：

  {{ (string)old('Priority_id') === (string)$priority->id ? 'selected' : '' }}
  

最终完整代码： #

<select id="Priority_id" name="Priority_id" style="width:180px;" class="myform-select">
    <option value="" {{ old('Priority_id') === null ? 'selected' : '' }}>Select priority</option>
    @foreach ($priorities as $priority)
        <option value="{{ $priority->id }}" {{ (string)old('Priority_id') === (string)$priority->id ? 'selected' : '' }}>
            {{ $priority->Desc }}
        </option>
    @endforeach
</select>

内容的提问来源于stack exchange，提问作者mahdi.gh