- preg_match: documentation ( source)
- str_replace: documentation ( source)
<?php
$input = 'S1G5AB'; // given this
$store = '5I6GAB'; // actually this
$regex = str_replace(['S','G','I'], ['[S5]', '[G6]', '[I1]'], $input);
echo $regex;
echo (0 < preg_match("/$regex/", $store) ? 'Match' : 'No match');