How Do I make Global Scope Variables Available to Functions

I am writing a PHP script that has a number of variables that (I think) are in Global scope; that is, they are defined inline before the first command of the script. Note that these are not necessarily constants as shown in the example I included; most of them can be changed by the script. I have functions defined following these variables and before the commands in the script appear, but when they are called, the functions report the variables as undefined. This means I have to pass all the Globals to each function as a call argument. A trivial script illustrating the problem is below. This seems odd but I don't see what I am doing wrong. Any suggestions? PHP 5.6.30 called through php-fpm on Apache. Thanks in advance. John ------------------------------------ test.php - working version This variant passes a variable in global scope explicitly as a parameter. It displays correctly on the browser screen. <?php $bad_line = "This line should display on screen."; // sample function that works function sample1($bad_line) { return "\n" . $bad_line . "\n"; } // this call does work echo sample1($bad_line); exit; ?> test.php - doesn't work This variant does not work; it throws error: [Sun May 27 20:17:46.779348 2018] [proxy_fcgi:error] [pid 893:tid 139838497978112] [client 192.168.1.104:37732] AH01071: Got error 'PHP message: PHP Notice: Undefined variable: bad_line in /httpd/iliffe/yrarc/test.php on line 8\n' <?php $bad_line = "This line should display on screen."; // sample function that doesn't work function sample1() { return "\n" . $bad_line . "\n"; } // this call doesn't work echo sample1(); exit; ?>