reveal_ajax.js

(function($) {

	$.fn.displayPost = function() {
		event.preventDefault();
		var post_id = $(this).data("id");
		var id = "#" + post_id;

		// Check if the reveal modal for the specific post id doesn't already exist by checking for it's length
		if($(id).length == 0 ) {
			// We'll add an ID to the new reveal modal; we'll use that same ID to check if it exists in the future.
			var modal = $('<div>').attr('id', post_id ).addClass('reveal-modal').appendTo('body');
		  	var ajaxURL = MyAjax.ajaxurl;
			 $.ajax({
		            type: 'POST',
		            url: ajaxURL,
		            data: {"action": "load-content", post_id: post_id },
		            success: function(response) {
			            modal.empty().html(response).append('<a class="close-reveal-modal">&#215;</a>').foundation('reveal', 'open');
			            modal.bind('opened', function() {
			            	// Reset visibility to hidden and set display: none on closed reveal-modal divs, for some reason not working by default when reveal close is triggered on .secondary links	
			            	$(".reveal-modal:not('.reveal-modal.open')").css({'visibility': 'hidden', 'display' : 'none'})
			            	// Trigger resize 
		            		$(window).trigger('resize');
				        return false;
			  		});
		  	 	}
		   		});
			}
		 	//If the div with the ID already exists just open it.
		     else {
			$(id).foundation('reveal', 'open');
		     }

		     	// Recalculate left margin on window resize to allow for absolute centering of variable width elements in window
		     	$(window).resize(function(){
			    	var left;
				left = Math.max($(window).width() - $(id).outerWidth(), 0) / 2;
				$(id).css({
				left:left + $(window).scrollLeft()
			});
		});
	}

})(jQuery);

// Apply the function when we click on the .reveal and .secondary links in open modals
jQuery(document).on("click", ".reveal,.secondary", function() {
	jQuery(this).displayPost();

});

/* Close open modal via secondary paging links by retrieving parent div's id 
* Uses native foundation functions */
jQuery(document).on("click", ".secondary", function() {
	var id = jQuery(this).closest("div").attr("id");
	 jQuery(id).foundation('reveal', 'close');
});

Modified jeduan's script to allow WordPress Ajax to use Zurb Foundation's inbuilt modal display plugin Reveal, also centers reveal-modal window for variable sized content, includes paging navigation.