Determine source of non-ASCII characters from bin_to_str()

[sneurlax]

bin_to_str() currently* outputs errant non-ASCII characters, eg. '�'. I am successfully stripping them via preg_replace('/[[:^print:]]/', '', join($res));, but this feels hacky to me--we shouldn't be encountering non-ASCII characters at all. Perhaps it's an off-by-one error in the for loop parameters?

*Under certain circumstances (like with input string 0123456789ABCDEF)

[sneurlax]

Under current test conditions, this preg_replace(...) line can be completely removed (replaced with just join($res).) That resolves the hacky feeling I have, but doesn't satisfy this issue's stipulation to determine what the fuck was going on with the original test string (0123456789ABCDEF) that caused that errant SOH.

[sneurlax]

Yeah, $base58->encode('0123456789ABCDEF') == �C3CPq7c8PY. Weird.