function detectUTF8($string)
{
        return preg_match('%(?:
        [\xC2-\xDF][\x80-\xBF]        # non-overlong 2-byte
        |\xE0[\xA0-\xBF][\x80-\xBF]               # excluding overlongs
        |[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}      # straight 3-byte
        |\xED[\x80-\x9F][\x80-\xBF]               # excluding surrogates
        |\xF0[\x90-\xBF][\x80-\xBF]{2}    # planes 1-3
        |[\xF1-\xF3][\x80-\xBF]{3}                  # planes 4-15
        |\xF4[\x80-\x8F][\x80-\xBF]{2}    # plane 16
        )+%xs', $string);
}

function cp1251_utf8( $sInput )
{
    $sOutput = "";

    for ( $i = 0; $i < strlen( $sInput ); $i++ )
    {
        $iAscii = ord( $sInput[$i] );

        if ( $iAscii >= 192 && $iAscii <= 255 )
            $sOutput .=  "&#".( 1040 + ( $iAscii - 192 ) ).";";
        else if ( $iAscii == 168 )
            $sOutput .= "&#".( 1025 ).";";
        else if ( $iAscii == 184 )
            $sOutput .= "&#".( 1105 ).";";
        else
            $sOutput .= $sInput[$i];
    }
    
    return $sOutput;
}

function encoding($string){
    if (function_exists('iconv')) {    
        if (@!iconv('utf-8', 'cp1251', $string)) {
            $string = iconv('cp1251', 'utf-8', $string);
        }
        return $string;
    } else {
        if (detectUTF8($string)) {
            return $string;        
        } else {
            return cp1251_utf8($string);
        }
    }
}
echo encoding($string);