$newstring = trim($string, '/');

------解决方案--------------------
什么意思，没太搞懂。是不是第一个字符或者最后一个字符是/,就去掉
用trim函数

echo trim($str,'/');去掉首尾的‘/’字符

------解决方案--------------------
PHP code

$str="/Maildir/cur/usrp/";
$str = substr($str,0,1)=="/"?substr($str,1):$str;
$str = substr($str,-1,1)=="/"?substr($str,0,-1):$str;
echo $str;

$str="/////Maildir/cur/usrp/////";
$strarr=explode("/",$str);
foreach($strarr as $k=>$s){
    if($s=="")unset($strarr[$k]);
}
echo join("/",$strarr);