Setting multiple image urls using WordPress’ Media Uploader

There’re 2 things you should consider:

1. change send_to_editor inside click callback. This will change this function only when needed, e.g. when uploader is shown. This also prevent unwanted things with global variables.

2. You should always backup the send_to_editor.

Here’s my sample code (not tested):

jQuery(document).ready(function($) {
    $('#upload_image_button_main').click(function() {
        var backup = window.send_to_editor;

        window.send_to_editor = function(html) {
            imgurl = $('img', html).attr('src');
            jQuery('#_my_meta_upload_image_main').val(imgurl);
            tb_remove();
        };

        tb_show('', 'media-upload.php?type=image&TB_iframe=true');

        window.send_to_editor = backup;
        return false;
    });
});