php mb_strlen() Chinese and English mixed character interception code_PHP tutorial

function utf8substr($str, $from, $len) 
{ 
return preg_replace('#^(?:[x00-x7f]|[xc0-xff][x80-xbf]+){0,'.$from.'}'. 
'((?:[x00-x7f]|[xc0-xff][x80-xbf]+){0,'.$len.'}).*#s', 
'$1',$str); 
}

function gb2312_strlen($string)
{
$str_len = strlen($string);
$str_count = 0;
for($j = 0; $j < $str_len; $j++)
{
   if(ord($string{$j}) < 127)
   {
    $str_count += 1;
    continue;
   }
   else
   {
    if(ord($string{$j+1}) > 127)
    {
     $str_count += 1;
     $j++;
     continue;
    }
    else
    {
     $str_count += 1;
     continue;
    }
   }
}
return $str_count;
}
$str = "开s d";  
echo gb2312_strlen($str);