Question

I am working on a script that develops certain strings of alphanumeric characters, separated by a dash -. I need to test the string to see if there are any sets of characters (the characters that lie in between the dashes) that are the same. If they are, I need to consolidate them. The repeating chars would always occur at the front in my case.

Examples:

KRS-KRS-454-L
would become:
KRS-454-L

DERP-DERP-545-P
would become:
DERP-545-P

Answer 1

<?php
$s = 'KRS-KRS-454-L';
echo preg_replace('/^(\w+)-(?=\1)/', '', $s);
?>
// KRS-454-L

This uses a positive lookahead (?=...) to check for repeated strings.

Note that \w also contains the underscore. If you want to limit to alphanumeric characters only, use [a-zA-Z0-9].

Also, I’ve anchored with ^ as you’ve mentioned: “The repeating chars would always occur at the front […]”