getenv

getenv -- Get the value of an environment variable

Description

string getenv(string varname);

Returns the value of the environment variable varname, or false on an error.

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  2 $ip = getenv("REMOTE_ADDR"); // get the ip number of the user 
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You can see a list of all the environmental variables by using phpinfo(). You can find out what many of them mean by taking a look at the CGI specification, specifically the page on environmental variables.