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Core PHP Programming, Third Edition by Leon Atkinson

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7.4. Environment Variables

PHP also makes environment variables available. These are the variables that are created when you start a new shell. Some are the standard variables like PATH. Others are variables defined by the CGI. Examples are REMOTE_ADDR and HTTP_USER_AGENT. PHP adds them all to the _SERVER array for your convenience.

Similar to environment variables are the variables that PHP itself creates for you. The first is GLOBALS, which is an associative array of every variable available to the script. Exploring this array will reveal all the environment variables as well as a few other variables. Similar to GLOBALS are _GET, _POST, _COOKIE, _SERVER, and _REQUEST. As their names suggest, they are associative arrays of the variables created ...

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