<?php
$alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$offset = 1;
$limit = 6;
$start = max(0, $offset-$limit);
$end = min(strlen($alpha)-1, $offset+$limit);
Echo substr($alpha, $start, $end-$start+1);
/*
To output them one by one as in an array you can use this:
$result = substr($alpha, $start, $end-$start+1);
For($i=0; $i<strlen($result); $i++){
Echo $result[$i] . "\n";
}
Or you can explode("", $result); to make it a true array
*/