Creative (crazy) uses of Chain Assignment (PHP)

by Praveen Kumar Purushothaman

I was working on a registration screen and had to send some information to the database controller. I had the following code:

$_POST["Username"] = SanitizeData($_POST["Username"]);
$_POST["Password"] = SanitizeData($_POST["Password"]);
$_POST["FullName"] = SanitizeData($_POST["FullName"]);
$_POST["Email"]    = SanitizeData($_POST["Email"]);
// Send data to the controller.
sendData($_POST);

What if the $_POST had more fields, say, $_POST["submit"] or something, which could be common. So, I made a new array and sent the data this way:

$data = array();
$data["Username"] = $_POST["Username"] = SanitizeData($_POST["Username"]);
$data["Password"] = $_POST["Password"] = SanitizeData($_POST["Password"]);
$data["FullName"] = $_POST["FullName"] = SanitizeData($_POST["FullName"]);
$data["Email"]    = $_POST["Email"]    = SanitizeData($_POST["Email"]);
// Send data to the controller.
sendData($data);

Now I can be happy that I am sending only the fields in the array I need and nothing else. While doing this, I was thinking what other crazy uses can this have. I looked into a few examples online and found this piece of gem. 💎

Basic Version

What if the right side constant changes, it will be helpful not to reinitialise it again and again for more variables.

$a = $b = $c = 2;
// Ah, we need it as 3!
$a = $b = $c = 3;

What if this 2 gets changed into 3? There will be only one character change in the above, while in the traditional ones, you have to change three entries of 2 into 3:

$a = 2;     $a = 3;
$b = 2;     $b = 3;
$c = 2;     $c = 3;

Craziness #1

The previous code can be guessed by many people. One crazy example I saw online was using a loop. Do you want a single loop with one positive numbers and one negative numbers? Here you go.

for ($i = $j = 0; $i < 5; $i++, $j--)  
  echo "$i    $j\n";

The output is crazy like:

0    0
1   -1
2   -2
3   -3
4   -4

Craziness #2

If you think the above is not crazy enough, check this out. Let's say you have two operations happening in a single line of code:

$a = ($b = 1) - 1;

This will leave you with two values:

$a = 0;
$b = 1;

So what exactly happens in the above code is that, you assign 1 to $b, and the whole assignment operation acts like a return of a immediately invoked function expression that returns the value that was set, which is 1. And with that, if you subtract another 1, you get 0 and that's set to $a.

I haven't seen such crazy uses with chained assignments and it baffled me. So this post. Share your crazy findings in the comments. Until next time! 😁