php去掉字符串的最后一个字符附substr()和mb_substr()的用法

<span style="font-size:18px;">$str = "1,2,3,4,5,6,";
$newstr = substr($str,0,strlen($str)-1);
echo $newstr; </span>

$get_city='梧州市';
$get_city=mb_substr($get_city,0,strlen($get_city)-3);
echo $get_city;