<?php $x = 5; $y = 10; function myTest() { global $x, $y; $y = $x + $y; } myTest(); // run function echo $y; // output the new value for variable $y ?> <?php $x = 3; $y = 2; function myTest() { $GLOBALS['y'] = $GLOBALS['x'] + $GLOBALS['y']; } myTest(); echo $y; // 5 ?> define("GREETING", "mysite.com"); function myTest() { echo GREETING; } myTest(); // mysite.com