Encoding detection is not supported for windows-1252
. According to the mb_detect_order documentation:
mbstring currently implements the following encoding detection filters. If there is an invalid byte sequence for the following encodings, encoding detection will fail.
UTF-8, UTF-7, ASCII, EUC-JP,SJIS, eucJP-win, SJIS-win, JIS, ISO-2022-JP
For ISO-8859-, mbstring always detects as ISO-8859-.
For UTF-16, UTF-32, UCS2 and UCS4, encoding detection will fail always.