getenv()

getenv() — Gets the value of a single or all environment variables.

You can see a list of all the environmental variables by using phpinfo. Many of these variables are listed within RFC 3875, specifically section 4.1, “Request Meta-Variables”.

Inputs: name: The variable name as a string or null. local_only: When set to true, only local environment variables are returned, set by the operating system or putenv. It only has an effect when name is a string.

Returns: Returns the value of the environment variable name, or false if the environment variable name does not exist. If name is null, all environment variables are returned as an associative array.