写入时不能使用函数返回值

Question

I got new one problem with empty or trim function. I guess trim cant return a boolean but I dont know why ? :c

$author = htmlentities($_POST['author']);
        if(empty(trim($author))) $author="Unknown";

Gives me this error:

Fatal error: Can't use function return value in write context

Answer 1

Trim the string variable separately. trim() can not return a boolean value as it returns a string value. If you mean that empty() combined with trim() can't return a boolean value, I think that is weird and should work. Try this:

$author = htmlentities($_POST['author']);

$author = trim($author);
if(empty($author)){ 
    $author = "Unknown";
}