Encrypting with Arrays

Beginners - Learning PHP
#1

I am an absolute neophyte, so please bear with me. I am trying to decipher a bit of code that is used on our website that changes a number to a code for use with a shortened URL. We start with a number that links to a specific page on the website, encode it and then append it to a URL. I cannot find how the encoding function works. The number to encode is anything between a one and seven digit number. Here is the function that encodes the number:

function encryptZip($zip) {    
	$theSource = Array("8","v","w","M","P","I","N","o","Z","h","g","_","u","W","D","-","b","O","k","a","G","t","U","j","6","7","K","A","r","y","l","5","X","p","n","z","F","4","Y","d","2","9","q","V","s","0",".","e","H","c","x","Q","B","S");    	
	$r = '';    	
	while ($zip>0){    		
		$num = $zip % 53;    		
		$zip = ($zip - $num) / 53;    		
		$r .= $theSource[$num];    	
	}    	
	return $r;    
}

Thanks in advance for any help,
RDW

#2

What do you think it does?

You have the encryption key, and how it arrives at the values, how it builds the new string.

#3

This is my problem. Somehow this takes a number like 1234567 and returns it as a short code, for example “1471463” becomes “6s.h” (no quotes). I feel like I’m missing something here but it is basically the same function that decodes it on the other end.

#4

Step thru it.

It pulls the number apart; does some math on it; then uses that as a key to what character to replace it with.

#5

This is good…a start for my education in array usage. But I am truly a neophyte and while I understand the part about doing the math on it (although I don’t know where 53 came from), I don’t get how that array is sequentially converting a one to seven digit number to a uniform four digit code that can be de-encrypted back to however many digits. I’m baffled.

The goal of this is, first of all to understand how it works but temporarily to build a function or a formula in Excel that I can give some of my workmates to do some ad hoc conversions for producing some one-off URLs that can be decoded by our website.

#6

Run the code in its individual parts to see what each things does.

#7

Thanks Astonecypher, I will try that

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