- array_map: documentation ( source)
- str_split: documentation ( source)
<?php
$KEY_BASE = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
$BASE = 62;
$num = 11112887;
$num = array_map('intval',str_split($num));
foreach ($num as $digit) {
echo $digit;
}