Php operator substr and assignment return empty variable?

Question

PHP

There is a cycle

foreach($array_pages as $v)
{
    $quantity_elements++;
    if (!empty($v['URL'])) {
        $vUrl = substr($v['URL'], -1);
        if ($vUrl != '/') {
            $v['URL'] = $v['URL'] + '/';
            print_r($v['URL']);
        }
    }
}

at the end, the $v['URL'] variable returns the / sign.
Initially, the $v['URL'] variable contains a link (for example, www.site.ru/news)
Next comes the condition where it is checked whether there is a slash at the end, and if so, it should return a link with a / at the end, but it returns just the / sign, as if $v['URL'] is empty. Where is the mistake?

An example of how it should display if there is no sign at the end /
www.site.ru/news/
If there is a sign / at the end of the link, then the condition does not work and goes further

Answer 1

In php, the concatenation operation is ., not +.

Answer 2

The answer is already there, but for the future to the author, wardump variables and there will be fewer questions