Variable Scope in PHP

Many Times Globality of variables will be the small issue, after long time I decided to use super globals. Super globals exists any where: $_SERVER, $_GET, $_POST ..... Now for example:
<?php
$foo
[] = range(03);
$_POST['foo'] = $foo;
a(); //no parameters needed.
b();
$foo $_POST['foo'];

Print_r($foo);
/* out

Array
(
    [0] => Array
        (
            [0] => 0
            [1] => 1
            [2] => 2
            [3] => 3
        )

    [1] => Array
        (
            [0] => 4
            [1] => 5
            [2] => 6
            [3] => 7
        )

    [2] => Array
        (
            [0] => 8
            [1] => 9
            [2] => 10
        )

)

*/
function a(){
    
$_POST['foo'][] = range(47);
}

function 
b(){
$_POST['foo'][] = range(810);
}
?>
Note: the key must not be passed by the page via _POST method by the form, else the value will be over written