JuniorTheoryCommon

What does the program print?

PHP

<?php

$a = 5;
$b = $a;
$a = $a + 1;
echo $a, ' ', $b, "\n";

6 5

Expecting 6 6, as if $b were a second name for $a: $b = $a copies the value at that moment, and a later change to $a does not reach $b.
Expecting $a = $a + 1 to leave $a at 5: PHP computes $a + 1 from the old value and writes the result back into $a.

What does the program print if $b = $a; becomes $b = &$a;?
Does $b = $a copy a large array at once, and when does PHP make the real copy?