<?php

$var = 1;

function local()
{
    global $var;
    $var = 2;
}

function localUnset()
{
    global $var;
    $var = 3;
    unset($var);
}

function globals()
{
    $local = $GLOBALS;
    $local['var'] = 4;
}

function globalsUnset()
{
    $local = $GLOBALS;
    $local['var'] = 5;
    unset($local);
}

function globalsFinalUnset()
{
    $GLOBALS['var'] = 6;
    unset($GLOBALS['var']);
}

function globalsFullUnset()
{
    unset($GLOBALS);
}
local();
var_dump($var);

localUnset();
var_dump($var);

globals();
var_dump($var);

globalsUnset();
var_dump($var);

globalsFinalUnset();
var_dump($var);

$var = 'fresh';
globalsFullUnset();
var_dump($var);

unset($GLOBALS);
var_dump($var);

int(2)
int(3)
int(4)
int(5)
NULL
string(5) "fresh"
string(5) "fresh"