Typically, for passing arguments to a command line script, you will use either the argv global variable or getopt:
// Bash command:
// php -e myscript.php hello
echo $argv[1]; // Prints "hello"
// Bash command:
// php -e myscript.php -f=world
$opts = getopt('f:');
echo $opts['f']; // Prints "world"
$_GET refers to the HTTP GET method parameters, which are unavailable on the command line, since they require a web server to populate.
If you really want to populate $_GET anyway, you can do this:
// Bash command:
// export QUERY_STRING="var=value&arg=value" ; php -e myscript.php
parse_str($_SERVER['QUERY_STRING'], $_GET);
print_r($_GET);
/* Outputs:
Array(
[var] => value
[arg] => value
)
*/
You can also execute a given script, populate $_GET from the command line, without having to modify said script:
export QUERY_STRING="var=value&arg=value" ; \
php -e -r 'parse_str($_SERVER["QUERY_STRING"], $_GET); include "index.php";'
Note that you can do the same with $_POST and $_COOKIE as well.