UNICODE to UTF-8 encoding

From http://www.php.net/manual/en/function.chr.php#55978:

"I spent hours looking for a function which would take a numeric HTML entity value and output the appropriate UTF-8 bytes.  
I found this at another site and only had to modify it slightly; so I don't take credit for this."

<?php function unichr($dec) { 
  if ($dec < 128) { 
    $utf = chr($dec); 
  } else if ($dec < 2048) { 
    $utf = chr(192 + (($dec - ($dec % 64)) / 64)); 
    $utf .= chr(128 + ($dec % 64)); 
  } else { 
    $utf = chr(224 + (($dec - ($dec % 4096)) / 4096)); 
    $utf .= chr(128 + ((($dec % 4096) - ($dec % 64)) / 64)); 
    $utf .= chr(128 + ($dec % 64)); 
  } 
  return $utf;
} ?>

So for example:

<?php

  $str = "Chinese: &#20013;&#25991;";
  $str = preg_replace("/&#(\d{2,5});/e", "unichr($1);", $str);

?>