PHP - 将vars与字符串组合以创建一个字符串[关闭]

So basically I am trying to save something on my root folder:

$xml->save('../datas/' + $randomString + '.xml');

But it doesn't work. however, when I do

$xml->save('../datas/hi.xml');

it does. so I figured, it must be a problem with my var, randomString:

$randomString = substr(str_shuffle("0123456789"), 0, $length);

So, what am i doing wrong?

You want string concatenation. In PHP the operator for it is ., not +.