php 截取中文字符

<?php
/*
*截取字符串
*bilibo@2011-06-23
*/
class StringHelper extends AppHelper {
function CutStr($string, $sublen, $start = 0, $code = 'UTF-8') {
    
    
    if($code == 'UTF-8') {
   
    $pa = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|\xe0[\xa0-\xbf][\x80-\xbf]|[\xe1-\xef][\x80-\xbf][\x80-\xbf]|\xf0[\x90-\xbf][\x80-\xbf][\x80-\xbf]|[\xf1-\xf7][\x80-\xbf][\x80-\xbf][\x80-\xbf]/";
    preg_match_all($pa, $string, $t_string);
   
    if( count( $t_string[0] ) - $start > $sublen ) {
   
    return join('', array_slice($t_string[0], $start, $sublen));
   
    }
   
    return join('', array_slice($t_string[0], $start, $sublen));
   
    } else {
   
    $start = $start * 2;
    $sublen = $sublen * 2;
    $strlen = strlen($string);
    $tmpstr = '';
   
    for($i=0; $i<$strlen; $i++) {
   
    if($i>=$start && $i<($start+$sublen)) {
   
    if(ord(substr($string, $i, 1))>129) $tmpstr.= substr($string, $i, 2);
   
    else $tmpstr.= substr($string, $i, 1);
    }
   
    if( ord( substr($string, $i, 1 ) ) > 129 ) $i++;
   
     }
     
     if( strlen($tmpstr) < $strlen )
     
     return $tmpstr;
     
     }
  
  }
}
?>