// This finally helped me to do the job, thanks to Blackbit, had to modify deprecated ereg:
// original comment: "Squirrelmail contains a nice function in the sources to convert unicode to entities:"

function charset_decode_utf_8 ($string) {
    /* Only do the slow convert if there are 8-bit characters */
    /* avoid using 0xA0 (\240) in ereg ranges. RH73 does not like that */
    if (!preg_match("/[\200-\237]/", $string)
     && !preg_match("/[\241-\377]/", $string)
    ) {
        return $string;
    }

    // decode three byte unicode characters
    $string = preg_replace("/([\340-\357])([\200-\277])([\200-\277])/e",
        "'&#'.((ord('\\1')-224)*4096 + (ord('\\2')-128)*64 + (ord('\\3')-128)).';'",
        $string
    );

    // decode two byte unicode characters
    $string = preg_replace("/([\300-\337])([\200-\277])/e",
        "'&#'.((ord('\\1')-192)*64+(ord('\\2')-128)).';'",
        $string
    );

    return $string;
}