I precise that I've checked "form-data" option in Postman to send data in my request. If I check "x-www-form-encoded' option, it works, but I can't send files whith this option, it's posible only with "form-data".
If you use POST, then PHP will do the decoding of the input. For others, the framework has to to it, and currently it does only support www-form-urlencoded, and no multipart-data (which is quite complex to parse).