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<?php

add_action( 'wp_head', '_custom_head_scripts' );
function _custom_head_scripts() {

	// Change this.
	$popup_id = 123; ?>

	<script type="text/javascript">
		(function ($) {
			if (document.cookie.match(/loading-popup=/)) {
				$('<style>#pum-<?php echo $popup_id; ?> {display: block;}</style>').appendTo($('head'));
			}
		}(jQuery));
	</script><?php
}

add_action( 'wp_footer', '_custom_footer_scripts' );
function _custom_footer_scripts() {

	// Change this.
	$popup_id = 123; ?>
	
	<script type="text/javascript">
		(function ($) {
			var $popup = $('#pum-<?php echo $popup_id; ?>');

			if (document.cookie.match(/loading-popup=/)) {
				$(document).ready(function () {
					setTimeout(function () {
						$popup.fadeOut();
					}, 1000);
					$.pm_remove_cookie('loading-popup');
				})
			}

		}(jQuery));
	</script><?php
}