PHP variables are local to functions by default. Use global $var to access global variables inside a function, or pass as parameters (preferred).
Defined with define() or const. Constants are global and cannot be changed.
static $count = 0 — persists between function calls.
<?php
$globalVar = "I am global";
function test() {
global $globalVar; // declare global
echo $globalVar;
}
// Constants
define("SITE_NAME", "LearnCode");
const VERSION = "1.0.0";
echo SITE_NAME; // LearnCode (no $)
echo VERSION; // 1.0.0
// Static
function counter() {
static $count = 0;
return ++$count;
}
echo counter(); // 1
echo counter(); // 2
echo counter(); // 3
?>