non utf-8 encoding causes POST to crash

[janmentzel]

issue: there is an issue with curl crashing when posting non-utf-8 characters (e.g. german umlauts) in strings (e.g. billing_address.last_name or card_holder)
The integration tests with german umlauts proove umlauts in utf-8 work.
e.g. testWpfCreate using "address1": "Kurfürstendamm 123" in its fixture

goal: throw a Hypercharge\ValidationError if users provides a string with non-utf8 special chars

solution: check encoding with iconv when validating strings.
this would be best done in json-schema validator, adding a new param to string constraint "encoding":"utf8".

note: the crash is not as bad as it sounds. the payment/transaction would fail anyway when transmitting the data to the CC processor. better early than late.

[janmentzel]

a way to detect non-utf8 strings without iconv

<?php
function detectUTF8($string)
{
        return preg_match('%(?:
        [\xC2-\xDF][\x80-\xBF]        # non-overlong 2-byte
        |\xE0[\xA0-\xBF][\x80-\xBF]               # excluding overlongs
        |[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}      # straight 3-byte
        |\xED[\x80-\x9F][\x80-\xBF]               # excluding surrogates
        |\xF0[\x90-\xBF][\x80-\xBF]{2}    # planes 1-3
        |[\xF1-\xF3][\x80-\xBF]{3}                  # planes 4-15
        |\xF4[\x80-\x8F][\x80-\xBF]{2}    # plane 16
        )+%xs', $string);
}