PHP intercepts Chinese and English without garbled characters, including full-width characters

Code source: Xiaomo (self)
Complies with UTF-8, if it is under GBK
Change to $content .= $str[$sing].$str[$sing+1];
$sing += 3; changed to $sing += 2;

 /**
 * Chinese and English interception
 * @param string The string to be intercepted
 * @param string The length to be intercepted (exceeding the total length will be calculated as the total length)
 * @param [string] (optional) starting position (the first one is 0)
 * @return string
 * @author Xiaomo 244349067@qq.com
*/
 function mixSubstr($str, $length, $start=FALSE)
{
 if( ! $length){
 return false;
 }

 $strlen = strlen( $str);
 $content = '';
 $sing = 0;
 $count = 0;

 if($length > $strlen) {
 $length = $strlen;
 }
 if($start > ;= $strlen) {
 return false;
 }

 while($length != ($count-$start))
 {
 if(ord($str[$sing]) > 0xa0) {
 if( !$start || $start <= $count) {
 $content .= $str[$sing].$str[$sing+1].$str[$sing+2];
 }
 $sing + = 3;
 $count++;
 }else{
 if(!$start || $start <= $count) {
 $content .= $str[$sing];
 }
 $sing++;
 $count++;
 }
 }
 return $content;
}