Tag Archives: Ajax

PHP Script to fix AJAX Access-Control-Origin Errors

February 23, 2011 8:26 pm /

If you have an AJAX application that uses a PHP back-end app on a different server as your web front-end server (e.g. load balancing, cdn’s, etc), your PHP script will need to send header variables with the allowed content server name(s).

Web browsers are now following a standard for HTTP Access control to prevent client-side Cross Site scripting attacks.

I tested this with Firefox and it simply blocks the request without any error messages. Google Chrome browser will error out with the following message if the access control origin is not set correctly on your PHP script. (woot!)

“XMLHttpRequest cannot load [PHP URL].. Origin [JAVASCRIPT URL] is not allowed by Access-Control-Allow-Origin.”

For example, if the Javascript is hosted on example.com and your PHP app is on example.org.

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Posted in: AJAX, PHP / Tagged: , ,

Internet Explorer cache and AJAX

February 10, 2009 8:38 pm /

The cache in Internet Explorer is not very AJAX friendly for GET/POST commands. You must put in a constantly changing variable in the URL such as date with seconds in Internet Explorer. I noticed this when the refresh of my GET command would only work once in my window.setInterval(.. , .. ) function.  However, in Mozilla and Safari, my function was working perfect.

The solution to this is to append the current date and time into the URL of your GET/POST request. Special thanks to this post.

...

var requeststring = "http://........."+"&requesttime=" + new Date().getTime();
myHttpObject.open("GET",requeststring,true);

...

 

I previously tried setting the cache to expire on the PHP header files, but it has no effect. However, this date/time trick works.

Posted in: AJAX / Tagged: , ,