将功能应用于每个div

so basically I have n divs which hold comments, just like on facebook, and in Jquery I have a function that run an ajax call that gets the comments for every div, at least that's what I want it to do, it only fetches the comments for the first div on the page, how do I make the function run for each div simultaneously ?

Here is the code: Ajax

interval = setInterval(function(){
    comment_id = $("#main-photo"+k).attr("commentid");
    k = $("#main-photo"+k).attr("nr_crt");
    $.post('../utility/countcomm.php', { comment_id: comment_id } , 
        function(output) {
            if (+total1 < +output)
                total1 = output;
            if (+total1 > +total2)
            {   
            $.post('../utility/fetchcomments.php', { comment_id: comment_id, start:total2, end:total1 } , 
                function(output1) {
                    $(".comment_append"+k).append("<p class='comment'>"+output1+"</p>");
                    var scrolldown = $('.comment_append'+k)[0].scrollHeight;
                    $('.comment_append'+k).animate({scrollTop:scrolldown}, 200);
                });
            total2 = total1;
            }
        });
},100);

HTML:

<div id="comment_box">
    <input type="text" name="comment" id="type_comment" value="Type a comment." />
    <div id="comment_append" class="comment_append<?php echo $k; ?>">

    </div><!--comment_append end-->
    <img id="main-photo<?php echo $k; ?>" nr_crt="<?php echo $k; ?>" class="main-photo" src="<?php echo $user_uploads['pic1'] ?>" width="<?php echo $width; ?>"  height="<?php echo $height; ?>" commentid="<?php echo $user_uploads['comment_id']; ?>"/>
</div><!--comment_box end-->

Every div has a different id assigned dynamically in php. Thank you.

When I read/understand your code correctly, you want to look for all images with the class main-photo, get the commentid and update the related div? In that case you need a loop over all images with that class:

interval = setInterval(function(){
    // loop over all images with the class
    $(".main-photo").each( function() {
        // get the comment_id and k (the unique part of the id)
        var $element = $(this),
            comment_id = $element.attr("commentid"),
            k =  $element.attr("nr_crt");
        // the rest is unchanged...
        $.post('../utility/countcomm.php', { comment_id: comment_id } , 
        function(output) {
            if (+total1 < +output)
                total1 = output;
            if (+total1 > +total2)
            {   
            $.post('../utility/fetchcomments.php', { comment_id: comment_id, start:total2, end:total1 } , 
                function(output1) {
                    $(".comment_append"+k).append("<p class='comment'>"+output1+"</p>");
                    var scrolldown = $('.comment_append'+k)[0].scrollHeight;
                    $('.comment_append'+k).animate({scrollTop:scrolldown}, 200);
                });
            total2 = total1;
            }
        });

    });
},100);

By the way, you should think about your periodic refresh settings (100 ms) will produce a huge amount of server requests. Depending on the amount of data, it could cause some problems.