PHP super global variable list
$ _ Get [] Get the variable array submitted using the get Method
$ _ Post [] Get the variable array submitted using the POST method
$ _ Cookie [] obtain and set the cookie ID of the current website
$ _ Session [] gets the unique identifier of the current user's access, represented in arrays, such as sessionid and custom session data.
$ _ Env [] current PHP environment variable array
$ _ Server [] current PHP server variable array
$ _ FILES [] parameter values submitted to the current script during file upload, in array format
$ _ Request [] contains all requests submitted by the current script,
All actions of $ _ Get, $ _ post, $ _ cookie, and $ _ Session
$ Globals [] contains references to all super global variables in the script being executed
PHP system constant
_ File _ current PHPProgramAbsolute script path and file name
_ Line _ stores the row number of the constant
_ Function _ name of the function where the constant is stored
_ Class _ stores the name of the class where the constant is located.
_ Method _ name of the method that stores the class of the constant
Php_version stores the current PHP version, which can also be obtained through the phpversion () function.
Php_ OS stores the operating system of the current server