以ASCII格式转换UTF-8重音符号

I saw there are different discussion on this subject and I did find some solutions, but I still can't fix the accent problem.

I have a text in Italian, we have some letters with accents (à, è, é, ì, ò and ù), this text gets sent in a file over to another website and this has to be in ASCII format, this is what I'm currently doing:

$res_to_write = "Non c'è più l'oblò, è lì o là?" //DEMO TEXT
$resfile = iconv("UTF-8", "US-ASCII//TRANSLIT", $res_to_write);

The result is in ASCII, which is good but it gets converted to:

Non c'e piu l'oblo, e li o la?

Which is completely wrong in Italian.

Do I have to make a replace of every accent like è => e' (single quote) so at least looks ok or there is another solution to this?

As of now I don't have other solutions other than replace it with an apostrophe:

$res_to_write = "Non c'è più l'oblò, è lì o là?" //DEMO TEXT
$res_to_write = str_replace(['à', "è", "é", "ì", "ò", "ù"], ["a'", "e'", "e'", "i", "o'", "u'"], $res_to_write);
$resfile = iconv("UTF-8", "US-ASCII//TRANSLIT", $res_to_write);