What is a header? Especially, what are POST@GET headers?

This might help you This blog post may help:
http://blog.httpwatch.com/2007/12/10/two-simple-rules-for-http-caching/

To fix the issue you can do I posted an example here an how to support decoration views. It would be similar for supplementary views, with the following differences:
Instead of registering the NIB or class on the layout you would call – registerClass:forSupplementaryViewOfKind:withReuseIdentifier: on the UICollectionView instance In your view controller for the UICollectionView you would implement – collectionView:viewForSupplementaryElementOfKind:atIndexPath: similar to the method for normal cells In the layout subclass you need to implement the following method – layoutAttributesForSupplementaryViewOfKind:atIndexPath: to position the supplementary views at their positions In the – layoutAttributesForElementsInRect: make sure to add all the supplementary views you want (similar to the decoration view in the example I posted)

it should still fix some issue On this page I have a query to select then display a message, a query to delete a message and a query to add a message. When the query to delete a message and add a message run successfully I am redirecting back to the same page so the user can see the upadate. Because I need to pass a few variables when I do this I am using header redirect. , I think you can try a simple way for redirect your page :

echo "<script>window.location.href = $update_url</script>";

echo "<script>window.location.raplace('$update_url')</script>";

fixed the issue. Will look into that further You have indeed set the authorization header in the correct way. However, postservertest.com has prohibited that header from being used via Access-Control-Allow-Headers:

$ HEAD http://posttestserver.com
200 OK
Connection: close
Date: Wed, 06 Apr 2016 15:26:58 GMT
Server: Apache
Vary: Accept-Encoding
Content-Type: text/html; charset=UTF-8
Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept
Access-Control-Allow-Origin: *