How to use database settings from one file to whole site [duplicate]

This question already has an answer here:

• creating a separate file to connect to mysql with php 5 answers

I don't know it's possible or notm but if it's possible please tell how to do this.

I'm trying to code a students login website for my college. I want to use the database connection details like host name, password, user etc.,

I don't want to type this details in every page. I need to access these details from a predefined php configuration file to use around my site.

Please let me know how to do this.

And please forgive me for this terrific English.