String encoding for HTML

I find this a handy function to encompass a number of different string encoding routines. It allows you to do entity encoding (ÿ), hex (á), html (&aecute;), or url encoding (%E1).

It uses a number of defined constants for convenience.

/**
 * Encode a string for HTML usage
 *
 * This method will encode characters (such as accented characters, &,
 * >, and so on) to either their equivelant entities in decimal (ÿ),
 * hex (á) or html (&aecute;).  It can also be used to convert to
 * url encode, %E1.
 *
 * Encoding will only happen to characters greater than '~' (chr(127)).
 *
 * If an incorrect encoding type is passed it will simply return the
 * string in the same state.
 *
 * @param string $str The string to encode
 * @param integer $type The type of encoding to use
 * @return string
 * @access public
 */

define('ENC_TO_DEC', 0);
define('ENC_TO_HEX', 1);
define('ENC_TO_ENT', 2);
define('ENC_TO_URL', 3);

function encode_html($str, $type = ENC_TO_DEC)
{
    $result = '';
    switch($type) {
       case ENC_TO_ENT:
           $fixed = htmlentities($str, ENT_QUOTES);
           $trans = array();
           for ($i = 127; $i < 255; $i++) {
               $trans[chr($i)] = "&#{$i};";
           }
           $result = strtr($fixed, $trans);
           break;
       case ENC_TO_DEC:
           for ($i = 0; $i < strlen($str); $i++) {
               $cdec = ord($str{$i});
               $result .= ($cdec <= 127) ? $str{$i} : "&#{$cdec};";
           }
           break;
       case ENC_TO_HEX:
           for ($i = 0; $i < strlen($str); $i++) {
               $cdec = ord($str{$i});
               $result .= ($cdec <= 127) ? $str{$i} : '&#x' . strtoupper(dechex($cdec)) . ';';
           }
           break;
       case ENC_TO_URL:
           $result = urlencode($str);
           break;
       default:
           $result = $str;
           break;
    }
    return $result;
}