I'm quite sure that answer you get is not a solution for your problem. If it is true what you said, when file customers.php is not in the root of web directory, which means is hidden from url, then you can not solve problem with the help of $http.get function.
Suppose that we have
/var/www/public directory
and the file customers.php is in next directory
/var/customers.php
Your root directory of your web server is
/var/www/public
with your AngularJS files, like *.html or customers.html.
If someone enter this url
www.serverip.com
Your web server point to this directory
/var/www/public/customers.html
and you want to read file from /var/customers.php with $http.get fuction.
You can not do that.
You must put customers.php in the root of your web server. For instance, in the next directory
/var/www/public/customers.php
Thanks for your attention.