php封装方法字符串标点等字符截取不乱码

<?php  
 header("Content-type:text/html; charset=utf8");  
 function cut_str($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 ) $tmpstr.= "";   
 return $tmpstr;   
 }   
 }   
  
  
 $str="我slskjd!fl是总那地方拉伸款到即发";  
  
  
 echo cut_str($str, 8, 5);