jquery update div background element - php

Question

Alright not sure what to do and i am honestly bit lost. What I am trying to do is upload a file to site via jQuery and push it to PHP which then deletes original image file and makes a a copy of it called header.jpg and pushes it where it needs to go. That part works with no problem. The problem here is how would I go about updating the div element if the header.jpg image is the background?
Note: no matter what the img will always be header.jpg but it needs to be re-cached by browser and outputed to user without page refresh
Here is how the header div is layed out
<div id="headerEmpty"></div>
<div id="pageName">
<h2><?php echo $pageName; ?></h2>
</div>
<?php if ( $_SESSION['signed_in'] == true ) { ?>
<div id="header" style="background-image:url(uploads/header.jpg);">
<span class="edit" fn="header">
<img src="uploads/icon/16/018.png" />
</span>
<div class="fn_menu" style="display:none;"></div>
</div>
<?php } else { ?>
<div id="header"></div>
<?php } ?>
and here is the jquery bit which displays loader and auto-starts the upload process
$('#photoimg').live('change', function() {
$("#preview").html('');
$("#preview").html('<img src="uploads/icon/16/ajax-loader.gif" alt="Uploading...."/>');
$("#imageform").ajaxForm(
{
target: '#header',
success : function(data) {
$("#header").html(data).fadeIn('fast');
}
}).submit();
});

Answer 1

When you want to update the image, change it's source. You can append a time-stamp to the source so it will not come from the browser's cache. In PHP that would be something like:
<div id="headerEmpty"></div>
<div id="pageName">
<h2><?php echo $pageName; ?></h2>
</div>
<?php if ( $_SESSION['signed_in'] == true ) { ?>
<div id="header" style="background-image:url(uploads/header.jpg?_=<?php echo time(); ?>);">
<span class="edit" fn="header">
<img src="uploads/icon/16/018.png" />
</span>
<div class="fn_menu" style="display:none;"></div>
</div>
<?php } else { ?>
<div id="header"></div>
<?php } ?>
The time-stamp should just be ignored and the image will be downloaded each update.
Update
Ok, I see now that the background image is on the element you are replacing the HTML of. You could use jQuery to update the url() of the image:
success : function(data) {
var theDate = new Date();
$("#header").css('background-image', 'uploads/header.jpg?_=' + theDate.getTime()).html(data).fadeIn('fast');
}
You could also use PHP to output the #header element and use replaceWith() instead of .html():
success : function(data) {
$("#header").replaceWith(data).fadeIn('fast');
}
This assumes that your PHP output now looks like this:
<div id="header" style="background-image:url(uploads/header.jpg?_=1234567890);">
<span class="edit" fn="header">
<img src="uploads/icon/16/018.png" />
</span>
<div class="fn_menu" style="display:none;"></div>
</div>