如何获取html表单的输入标签ID？

<?php
        $i = 1;
        $query1 = mysql_query("SELECT * FROM `alert_history` ORDER BY `alert_history`.`id` DESC LIMIT ".$start.",".$per_page."");
        while($result = mysql_fetch_array($query1)){
            echo '<td colspan = "2"><form method = "POST" onsubmit = "submitform()" ><textarea onFocus = "myFunction(1)" onBlur = "myFunction(0)" id = "comment'.$i.'" name = "comment"></textarea> <br />';
            echo '<input type = "text" id = "alertid'.$i.'" name = "alertid" value = "'.$result['id'].'">';
            echo '<input  type = "submit" name = "submit" value = "Comment" ></form></td>';
            $i++;
        }
?>


<script>
    function submitform(){
            var comment = $("#comment").val();
        var alertid = $("#alertid").val();
        alert(comment);
        $.ajax({
        type: "POST",
            url: "analytic.php",
            data:{cmt:comment,alert_id:alertid}
        });
            //return false;
      }
</script>
<?php
        $i = 1;
        $query1 = mysql_q