insert-通过Php程序 像数据库插入内容时。在页面提交之后，mysql会有两个相同的数据 只有id不同

mysqlinsertphp

if($action == 'insert'){ //接收数据 $title = empty($_POST['subject']) ? '' : $_POST['subject']; $content = empty($_POST['content']) ? '' : $_POST['content']; $user_id = $_SESSION['myuser']['id']; $create_ad = time(); $summary = empty($_POST['summary']) ? '' : $_POST['summary']; $category_id = empty($_POST['category_id']) ? '' : $_POST['category_id']; $cover = empty($_POST['cover']) ? 'mr.jpg' : $_POST['cover']; $state = empty($_POST['submit']) ? '' : $_POST['submit']; $is_delete = 0; $tags = ''; //验证 if($category_id == '' || $title == '' || $content = '' || $summary == ''){ header('refresh : 2 ; url = article.php?a=add'); echo '输入的信息有误，请重新输入'; exit; } //入库 $sql = "INSERT INTO tn_article VALUES(null, '$title','$content', $user_id, $create_ad, '$summary', $category_id, '$cover', '$state', '$is_delete', '$tags')"; //获取页面 if($dao ->query($sql)){ header('location:article.php?a=list'); exit; } else{ header('refresh : 2; url = article.php?a=add'); echo '添加失败'; exit; }}