php – codeigniter表单验证和数组作为字段名称

div class="grid_7">
                    <fieldset class="age shadow_50">
                        <label class="legend">Age Group</label>
                            <div class="formRow checkbox">
    <input id="" type="checkbox" name="age[]" value="child" />
    <label>Child</label>
</div>

                            <div class="formRow checkbox">
    <input id="" type="checkbox" name="age[]" value="30's" />
    <label>30s</label>
</div>
                            <div class="formRow checkbox">
    <input id="" type="checkbox" name="age[]" value="60's" />
    <label>60's</label>
</div>

                            <div class="formRow checkbox">
    <input id="" type="checkbox" name="age[]" value="teen" />
    <label>Teen</label>
</div>
                            <div class="formRow checkbox">
    <input id="" type="checkbox" name="age[]" value="40's" />
    <label>40's</label>
</div>

                            <div class="formRow checkbox">
    <input id="" type="checkbox" name="age[]" value="70's" />
    <label>70's</label>
</div>
                            <div class="formRow checkbox">
    <input id="" type="checkbox" name="age[]" value="20's" />
    <label>20's</label>
</div>

                            <div class="formRow checkbox">
    <input id="" type="checkbox" name="age[]" value="50's" />
    <label>50's</label>
</div>
                    </fieldset>
                </div>

我在我的控制器中设置了一个验证规则(在我看来)确保选中了一个复选框,

$this->form_validation->set_rules('age[]','age group','required|trim');

然而,当我测试这个时,我收到一个错误消息,因为姓名为age []的复选框我只想检查age []是否为空.

我怎样才能做到这一点？