I've found a solution. str_replace works right, but the problem was
that I get the string from a database and it seems that it was an
strange character (ascii 194), that had to be next to Β‘ or ΒΏ (ascii
161 and 191), I don't know why, but....
Now, to replace the Β‘ and ΒΏ, I must use
str_replace(array(chr(194).chr(161),chr(194).chr(191),"?","!"),"",
$literal);