Execution of global variable in php $_SERVER | Learning Curve- Perfect Tutorial for the beginers

<?php
$output_port=$_SERVER['REMOTE_PORT'];
print_r($output_port);  //51008

$output_agent=$_SERVER['HTTP_USER_AGENT'];
print_r($output_agent); //Mozilla/5.0 (Windows NT 6.1; WOW64; rv:26.0) Gecko/20100101 Firefox/26.0 

$output_method=$_SERVER['REQUEST_METHOD']; //GET
print_r($output_method); 


$output_host=$_SERVER['HTTP_HOST'];  //localhost
print_r($output_host); 


$output_adr=$_SERVER['REMOTE_ADDR'];  //127.0.0.1
print_r($output_adr); 



$output_self=$_SERVER['PHP_SELF'];  // /test/test.php 
print_r($output_self); 

?>

<?php

$output_port=$_SERVER['REMOTE_PORT'];

print_r($output_port); //51008

$output_agent=$_SERVER['HTTP_USER_AGENT'];

print_r($output_agent); //Mozilla/5.0 (Windows NT 6.1; WOW64; rv:26.0) Gecko/20100101 Firefox/26.0

$output_method=$_SERVER['REQUEST_METHOD']; //GET

print_r($output_method);

$output_host=$_SERVER['HTTP_HOST']; //localhost

print_r($output_host);

$output_adr=$_SERVER['REMOTE_ADDR']; //127.0.0.1

print_r($output_adr);

$output_self=$_SERVER['PHP_SELF']; // /test/test.php

print_r($output_self);