unicode 2 utf8

function unicode2utf8($c)
{
    $output="";
   
    if($c < 0x80)
    {
        return chr($c);
    }
    else if($c < 0x800)
    {
        return chr( 0xc0 | ($c >> 6) ).chr( 0x80 | ($c & 0x3f) );
    }
    else if($c < 0x10000)
    {
        return chr( 0xe0 | ($c >> 12) ).chr( 0x80 | (($c >> 6) & 0x3f) ).chr( 0x80 | ($c & 0x3f) );
    }
    else if($c < 0x200000)
    {
        return chr(0xf0 | ($c >> 18)).chr(0x80 | (($c >> 12) & 0x3f)).chr(0x80 | (($c >> 6) & 0x3f)).chr(0x80 | ($c & 0x3f));
    }
    return false;
}