How to use 'XAMPP' as a webserver and run a piece of php script?

[S©O®P1AN]

I have a piece of php script in a txt file, named script.php. I want to use XAMPP as a webserver, where do I paste the script.php file in the XAMPP program [I have currently placed the file in 'C:\xampp\htdocs'], and more importantly run the webserver.

The purpose of the program is to see whether the registration of a certain website is open, [the registration opens at random times for a short space of time, as to avoid to many members joining], the php script written will then send me an email to tell me, its open.
when I type
http://localhost/registration/script.php

the page cannot be displayed even after refreshing several times, but when I type:http://localhost/registration/script.php.txt

I can see the script.

192.168.0.254/script.php, this does not work either, do I need to run APACHE first?
I did not write the php script, so I have no idea of how to run the program code. But it does have a timer on the script.php txt file:

while(0<1){
if(is_open()){
notify();
exit;
} else{
sleep(900);
}
}