使用html格式在ISO-8859-1环境中发送波兰字符

I have the following problem:

I have a webpage with a ISO-8859-1 charset.

Inside this page i have a form with the argument

accept-charset="UTF-8"

The form will be send with the post method

Now i want to submit polish letters mixed with latin letters

test ł,ą,ę,ś,ć,ż,ź,ó test

And want to display the result with PHP.

I tried several combinations of mb_convert_encoding, utf8_encode / utf8_decode, iconv and everything else. But the display is not right.

I just want to say to the browser: the page charset is iso-8859-1 but this small area is UTF-8