function mystr($str,$str_len) {//剪取一定长度的字符串(字符串,剪取长度)
     if (strlen($str)<=$str_len) {
         return $str;
     }else return mysubstr($str,0,$str_len)."...";
}
function mysubstr($str, $start, $len) {//剪取一定长度的字符串(字符串,剪取长度)
     $tmps教程tr = "";
     $strlen = $start + $len;
     for($i = 0; $i < $strlen; $i++) {
         if(ord(substr($str, $i, 1)) > 0xa0) {
             $tmpstr .= substr($str, $i, 2);
             $i++;
         } else
         $tmpstr .= substr($str, $i, 1);
     }
     return $tmpstr;
}

function syssubstr($string,$length,$append = false)
{
if (strlen($string) < = $length )
{
return $string;
}
else
{
$i = 0;
while ($i < $length)
{
$stringtmp = substr($string,$i,1);
if ( ord($stringtmp) >=224 )
{
$stringtmp = substr($string,$i,3);
$i = $i + 3;
}
elseif( ord($stringtmp) >=192 )
{
$stringtmp = substr($string,$i,2);
$i = $i + 2;
}
else
{
$i = $i + 1;
}
$stringlast[] = $stringtmp;
}
$stringlast = implode("",$stringlast);
if($append)
{
$stringlast .= "...";
}
return $stringlast;
}
}

$string = "";
$length = "18";
$append = false;
echo syssubstr($string,$length,$append);

function bite_str($string, $start, $len, $byte=3)
{
     $str     = "";
     $count   = 1;
     $str_len = strlen($string);
     for ($i=0; $i<$str_len; $i++) {
         if (($count+1-$start)>$len) {
             $str   .= "...";
             break;
         } elseif ((ord(substr($string,$i,1)) <= 128) && ($count < $start)) {
             $count++;
         } elseif ((ord(substr($string,$i,1)) > 128) && ($count < $start)) {
             $count = $count+2;
             $i     = $i+$byte-1;
         } elseif ((ord(substr($string,$i,1)) <= 128) && ($count >= $start)) {
             $str   .= substr($string,$i,1);
             $count++;
         } elseif ((ord(substr($string,$i,1)) > 128) && ($count >= $start)) {
             $str   .= substr($string,$i,$byte);
             $count = $count+2;
             $i     = $i+$byte-1;
         }
     }
     return $str;
}

// test
$str = "1测试测试2测试测试3测试测试4测试测试";
echo $str;
echo "<br>".bite_str($str,0,20,2);//0为开始地址,20为结束地址2为类型上面说到的

function ccstrlen(＄str) #计算中英文混合字符串的长度
{
＄cclen=0;
＄asclen=strlen(＄str);
＄ind=0;
＄hascc=ereg("[xa1-xfe]",＄str); #判断是否有汉字
＄hasasc=ereg("[x01-xa0]",＄str); #判断是否有ascii字符
if(＄hascc && !＄hasasc) #只有汉字的情况
return strlen(＄str)/2;
if(!＄hascc && ＄hasasc) #只有ascii字符的情况
return strlen(＄str);
for(＄ind=0;＄ind<＄asclen;＄ind++)
{
if(ord(substr(＄str,＄ind,1))>0xa0)
{
＄cclen++;
＄ind++;
}
else
{
＄cclen++;
}
}
return ＄cclen;
}