What is the best way to get a configuration variable in PHP

Each server (Dev, QA, Prod) has a different IP address and URL. I would like to 开发者_开发问答write code so that it can pull that information (the URL for the particular server I am running the code on) from a configuration file and store it in a variable.

Preferably I would like to avoid having to read the information from a file on subsequent requests since the information should not be changing often.

What is the best way to accomplish this?

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Use the $_SERVER array to get the current server details

http://php.net/manual/en/reserved.variables.server.php