How to map (large) integer on (small in size( alphanumeric string with PHP? (Cantor?)
- by Glooh
Dear all,
I can't figure out how to optimally do the following in PHP:
In a database, I have messages with a unique ID, like 19041985. Now, I want to refer to these messages in a short-url service but not using generated hashes but by simply 'calculate' the original ID.
In other words, for example: http://short.url/sYsn7 should let me calculate the message ID the visitor would like to request.
To make it more obvious, I wrote the following in PHP to generate these 'alphanumeric ID versions' and of course, the other way around will let me calculate the original message ID.
The question is: Is this the optimal way of doing this? I hardly think so, but can't think of anything else.
$alphanumString = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_';
for($i=0;$i < strlen($alphanumString);$i++)
{
$alphanumArray[$i] = substr($alphanumString,$i,1);
}
$id = 19041985;
$out = '';
for($i=0;$i < strlen($id);$i++) {
if(isset($alphanumString["".substr($id,$i,2).""]) && strlen($alphanumString["".substr($id,$i,2).""]) 0) {
$out.=$alphanumString["".substr($id,$i,2).""];
} else {
$out.=$alphanumString["".substr($id,$i,1).""];
$out.=$alphanumString["".substr($id,($i+1),1).""];
}
$i++;
}
print $out;
