How can we say that $_SERVER is an array?

Answer 1

Car dump or print-r

Answer 2

vardump

Answer 3

try this
print_r($_SERVER);
you will get all variables of array inside of it,
$_SERVER : containing information such as headers, paths, and script locations
or try :
echo $_SERVER[SERVER_ADDR'] :
You will get the IP address of the server

many and many for more information you can visit this page and learn more :
http://php.net/manual/en/reserved.variables.server.php