we’ll go it with get_defined_vars() function. get_defined_vars returns multidimensional array with all defiend variables in PHP
here we go ; 

$array = get_defined_vars();
 
print_r($array);

if you want to find out only SERVER vars you can try this;

print_r($array["_SERVER"]);

if you want to see vars in regular

echo "<pre>";
print_r($array);
echo "</pre>";