Page Load - White "flash" inbetween pages

Question

There are two websites, one live one under development. I am porting a site to Zend Framework (for maintainability/integration purposes).

The original (live) site has seamless page loads - it will load, then update the content on the screen while keeping the background image, navigation etc on the page.

The ported site (development) "flashes" completely white for a brief moment then all of the content appears simultaneously.

From what I understand, this is not a FOUC (flash of unstyled content). The content on both of the sites always appears fully styles with all CSS rules. The two sites look identical when rendered, they use the same images, css, and HTML markup. The only difference is one (development) is being served by Zend Framework and the other (live) by procedural PHP.

What are the main causes for this, and is this a known bug/configuration issue with ZF? I've had this problem before without using ZF and did not resolve it.

Thanks for your help.

Answer 1

It's pretty common for frameworks to evaluate the controller logic and render the body of the page before outputting anything; this can lead to delays in data being sent to the client, where your old page (I'm guessing) dumps the header of the page immediately.

Answer 2

It could be your web server. Try comparing the HTTP headers of your servers with a web sniffer like http://web-sniffer.net/ and see if there's any difference in caching headers. If there is, then your browser is dumping everything and starting fresh, which could look almost like a FOUC in some circumstances.