Probably because you have error reporting turned off, and yet you echo a line and then try and do a header redirect.
Stop the redirect from happening.
If you see anything being returned such as the contents of
echo $check_selections ;
then go back and comment that out.
This blank page will be a recurring problem for you unless you turn on error_reporting:
- for your entire server -- as long as it is your DEV server -- not your LIVE server!
- or, for the directory you are working in
- or, each page/script you are working on
For the latter then temporarily add these lines to the top of your script and you will find many helpful messages arriving.
// delete these lines before publishing!
If you notice a lot of messages now arriving at the top of your scripts, then imagine that these lines are all polluting your error log on your live server ... not good when you want to track a particular error.
You can do a web search for each type of message to discover how to correct them, or just ask here.
If this guess of mine does indeed turn out to be correct (current form shows I am not doing too well in the guessing stakes at the moment ), that you do not have error reporting switched on, and you want to turn it on for your DEV server (that is best practice) then make the adjustments on your local php.ini file, restart your server and you are golden.
Search: Turn on error reporting php.ini