如果您的问题有多个答案（选择），我建议您进行两种不同的验证：
第一个在客户端，使用Javascript。
CodeIgniter中的第二个示例，创建一个自定义验证方法。如果没有应用程序的代码，创建一个示例并不容易，但这可能会有所帮助：

HTML（您应提交的表单的一部分）

<p>Question 1:</p>
<input type="checkbox" name="questions[0][]" id="choice_1_1" value="Choice 1 Value">
<label for="choice_1_1">Choice 1 to Question 1</label>
<input type="checkbox" name="questions[0][]" id="choice_1_2" value="Choice 2 Value">
<label for="choice_1_2">Choice 2 to Question 1</label>
<input type="checkbox" name="questions[0][]" id="choice_1_3" value="Choice 3 Value">
<label for="choice_1_3">Choice 3 to Question 1</label>

<p>Question 2:</p>
<input type="checkbox" name="questions[1][]" id="choice_2_1" value="Choice 1 Value">
<label for="choice_2_1">Choice 1 to Question 2</label>
<input type="checkbox" name="questions[1][]" id="choice_2_2" value="Choice 2 Value">
<label for="choice_2_2">Choice 2 to Question 2</label>
<input type="checkbox" name="questions[1][]" id="choice_2_3" value="Choice 3 Value">
<label for="choice_2_3">Choice 3 to Question 2</label>

<!-- etc... -->

代码引发器

<?php

class Example extends CI_Controller {

        public function index()
        {
                // Loading the CI form helper (optional)
                $this->load->helper('form');
                
                // The CI form validation library
                $this->load->library('form_validation');

                // Set other form validations here...

                // Set custom validations here...
                $this->form_validation->set_rules('questions[]', 'Questions', 'callback_questions_check');

                // Run the validations...
                if ($this->form_validation->run() == FALSE)
                {
                        // If the validations failed (or the form wasn't submitted)...
                }
                else
                {
                        // If everything is OK...
                }
        }

        public function questions_check($questions)
        {
                // Read questions[] field (works as an array)...
                foreach ($questions as $question)
                {
                        // Check if every question has two checkboxes checked (works as an array too)...
                        if (count($question) != 2)
                        {
                                // If not, set an error message and return FALSE...
                                $this->form_validation->set_message('questions_check', 'The {field} must have two values checked');
                                return FALSE;
                        }
                }

                // If there are no errors, return TRUE...
                return TRUE;
        }
}

正如我所说的，检查这段代码是否适合您的代码并不容易，但是如果您有任何疑问，可以在这里找到更多信息：http://codeigniter.com/userguide3/libraries/form_validation.html?highlight=validation#callbacks-your-own-validation-methods