Calculate the length of Chinese strings and intercept Chinese strings in PHP

When doing PHP development, due to my country’s language environment problems, we often need to deal with Chinese. In PHP, we all know that there are special mb_substr and mb_strlen functions that can intercept and calculate the length of Chinese. However, since these functions are not core functions of PHP, they may not be turned on. Of course, if you are using your own server, you only need to enable it in php.ini. If a virtual host is used and the server does not enable this function, then we need to write some functions suitable for our national conditions.

The following functions are quite easy to use. But you need to know that it must be used in a utf-8 environment.

Support gb2312, gbk, utf-8, big5 Chinese interception method

/*  
  
* 中文截取，支持gb2312,gbk,utf-8,big5  
  
*  
  
* @param string $str 要截取的字串  
  
* @param int $start 截取起始位置  
  
* @param int $length 截取长度  
  
* @param string $charset utf-8|gb2312|gbk|big5 编码  
  
* @param $suffix 是否加尾缀  
  
*/  
   
public function csubstr($str, $start=0, $length, $charset="utf-8", $suffix=true)   
   
{   
   
   if(function_exists("mb_substr"))   
   
   {   
   
       if(mb_strlen($str, $charset) <= $length) return $str;   
   
       $slice = mb_substr($str, $start, $length, $charset);   
   
   }   
   
   else  
   
   {   
   
       $re[&#39;utf-8&#39;]   = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|[\xe0-\xef][\x80-\xbf]{2}|[\xf0-\xff][\x80-\xbf]{3}/";   
   
       $re[&#39;gb2312&#39;] = "/[\x01-\x7f]|[\xb0-\xf7][\xa0-\xfe]/";   
   
       $re[&#39;gbk&#39;]          = "/[\x01-\x7f]|[\x81-\xfe][\x40-\xfe]/";   
   
       $re[&#39;big5&#39;]          = "/[\x01-\x7f]|[\x81-\xfe]([\x40-\x7e]|\xa1-\xfe])/";   
   
       preg_match_all($re[$charset], $str, $match);   
   
       if(count($match[0]) <= $length) return $str;   
   
       $slice = join("",array_slice($match[0], $start, $length));   
   
   }   
   
   if($suffix) return $slice."…";   
   
   return $slice;   
   
}