PHP Problem – 03

I have published the following problem on the “Developers Zone” board of my mobile community site, JOTIL21.net. I am sorry, none could answer the question. They all tried to make hypothesis instead of practically trying out the script. So, I am posting the solution here.

Question:
What’s the output of the following code? Explain the code.

<?php
$a = "1";
$b = &$a;
$b = "2$a";
echo $a;
?>

I am just shocked! If anybody just copy-pasted the code and tested out, they would have known the output is “21″.

Here’s the code explanations:

<?php
$a = "1"; // assign 1 to $a
$b = &$a; // $b references to $a
$b = "2$a"; // $b changes to "2$a" that is "21" since $a == 1
echo $a; // since $b is a reference to $a, $a == $b
?>

It couldn’t have been easier… Shame on you guys…