判断字符串是否为utf-8格式的函数

// 判断字符串是否是UTF8格式    
function is_utf8($string) {    
  
    // From http://w3.org/International/questions/qa-forms-utf-8.html    
    return preg_match('%^(?:    
    [x09x0Ax0Dx20-x7E] # ASCII    
    | [xC2-xDF][x80-xBF] # non-overlong 2-byte  
    | xE0[xA0-xBF][x80-xBF] # excluding overlongs    
    | [xE1-xECxEExEF][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 is_utf8  

function is_utf8($word)
{
  if (preg_match("/^([".chr(228)."-".chr(233)."]{1}[".chr(128)."-".chr(191)."]{1}[".chr(128)."-".chr(191)."]{1}){1}/",$word) == true || preg_match("/([".chr(228)."-".chr(233)."]{1}[".chr(128)."-".chr(191)."]{1}[".chr(128)."-".chr(191)."]{1}){1}$/",$word) == true || preg_match("/([".chr(228)."-".chr(233)."]{1}[".chr(128)."-".chr(191)."]{1}[".chr(128)."-".chr(191)."]{1}){2,}/",$word) == true)
  { return  true; }
  else
  {return false;}
}