Example of using php global variable global

$a = 1;
$b = 2;
function Sum()
{
global $a, $b; //Declared as a global variable inside
$b = $a + $b;
}
Sum();
echo $b;
?>

Result: 3 If there is no global variable global, the values ​​​​of $a and $b cannot be obtained within the method, so if you want to use external variables in the method, you need to declare the variable as a global variable first, and then you can use it.