What are php global variables?

Question

I want to use session to pass variables through pages using php.
Site structure is:
1. header.php
2. column.php
3. footer.php
4. index.php
Pages 1, 2 & 3 are included into the index.php.

In header.php page, there is a drop down, in which links(cities) are placed where users will select city.
Now, I want to do code to store selected values into a variable and pass to multiple pages.

Please help on this..

Answer 1

Global scope refers to any variable that is defined outside of any function. PHP also stores all global variables in an array called $GLOBALS[index]. Its index is the name of the variable. This array is also accessible from within functions and can be used to update global variables directly.

Answer 2

Hey, In php SUPERGLOBAL is class for variable like global and others,

$GLOBALS is a PHP super global variable which is used to access global variables from anywhere in the PHP script (also from within functions or methods). PHP stores all global variables in an array called $GLOBALS[index].
Here is the exammple of it:+

<?php
$s = 25;
$t = 50;
function subtraction()
{
$GLOBALS['v'] = $GLOBALS['t'] - $GLOBALS['s'];
} 
subtraction();
echo $v;
?>