单击上一个之后单击清除之前自动单击的PHP单选按钮

Question

我遇到了单选按钮的问题，当我点击上一个按钮并且它没有提交到数据库时，它会自动清除。我无法将其与数据库中的答案相匹配。我也得到了按钮下一个按钮的相同问题。

enter code here
<div class="container question">
                    <div class="col-xs-12 col-sm-7 col-md-7 ">
                    <p>
                    Online exam 
                    </p>
                    <hr>
                    <div class="well">
                    <div id="replace_question">
                        <form class="form-horizontal" role="form" id='login' method="post" action="result.php">

                        <?php
                        $number_question = $_POST['num_questions'];
                        $row = mysqli_query( $con, "select * from questions where category_id=$category ORDER BY RAND()");
                        $rowcount = mysqli_num_rows( $row );
                        $remainder = $rowcount/$number_question;
                        $i = 0;
                        $j = 1; $k = 1;
                        ?>
                        <?php while ( $result = mysqli_fetch_array($row) ) {
                             if ( $i == 0) echo "<div class='cont' id='question_splitter_$j'>";?>
                            <div id='question<?php echo $k;?>' >
                            <p class='questions' id="qname<?php echo $j;?>"> <?php echo $k?>.<?php echo $result['question_name'];?></p>
                            <?php if (isset($result['answer1'])){?>
                            <input type="radio" value="1" id='radio1_<?php echo $result['id'];?>' name='<?php echo $result['id'];?>'/><?php echo $result['answer1'];?>
                            <br/>
                            <?php }?>
                            <?php if(isset($result['answer2'])) {?>
                            <input type="radio" value="2" id='radio1_<?php echo $result['id'];?>' name='<?php echo $result['id'];?>'/><?php echo $result['answer2'];?>
                            <br/>
                            <?php }?>
                            <?php if(isset($result['answer3'])){?>
                            <input type="radio" value="3" id='radio1_<?php echo $result['id'];?>' name='<?php echo $result['id'];?>'/><?php echo $result['answer3'];?>
                            <br/>
                            <?php }?>
                            <?php if(isset($result['answer4'])){?>
                            <input type="radio" value="4" id='radio1_<?php echo $result['id'];?>' name='<?php echo $result['id'];?>'/><?php echo $result['answer4'];?>
                            <br/>
                            <?php }?>
                            <input type="radio" checked='checked' style='display:none' value="5" id='radio1_<?php echo $result['id'];?>' name='<?php echo $result['id'];?>'/>                                                                      
                            <br/>
                            </div>
                            <?php
                            break;


                             } ?>   
                             </div>
                             </div>
                            </form>
                             <hr>
                             <input type="hidden" name="cur_ques_no" id="cur_ques_no" value="1">
                             <button id="1" class='previous btn btn-primary' type="button">Previous</button>
                             <button id="1" class="next btn btn-primary" type="button">Next</button>

                             </div>
                             </div>
                             </div>

如何解决此问题，请帮我解决以下代码。