自个儿实现phpUTF8中文字符串截取

header("Content-type: text/html; charset=utf-8");
function my_substr($str,$begin,$length){
$i = $begin;
$result="";
while($length > 0){
if([color=red]ord($str[$i])>127[/color]){
$result .= substr($str,$i,3);
$i = $i+3;
}else{
$result .= substr($str,$i,1);
$i++;
}
$length--;
}
return $result;
}
$chinese = "中a国people";
echo "<br>".my_substr($chinese,0,3);