PHP用str_replace（）替换URL段;

I have "/foo/bar/url/" coming straight after my domain name.

What I want is to find penultimate slash symbol in my string and replace it with slash symbol + hashtag. Like so: from / to /# (The problem is not how to get URL, but how to handle it)

How this could be achieved? What is the best practice for doing stuff like that? At the moment I'm pretty sure that I should use str_replace();

UPD. I think preg_replace() would be suitable for my case. But then there is another problem: what should regexp look like in order to make my issue solved?

P.S. Just in a case I'm using SilverStripe framework (v3.1.12)

$url = '/foo/bar/url/';

if (false !== $last = strrpos($url, '/')) {
    if (false !== $penultimate = strrpos($url, '/', $last - strlen($url) - 1)) {
        $url = substr_replace($url, '/#', $penultimate, 1);
    }
}

echo $url;

This will output

/foo/bar/#url/

If you want to strip the last /:

echo rtrim($url, '/'); // print /foo/bar/#url

Here is a method that would function. There are probably cleaner ways.

// Let's assume you already have $url_string populated
$url_string = "http://whatever.com/foo/bar/url/";

$url_explode = explode("\\",$url_string);
$portion_count = count($url_explode);

$affected_portion = $portion_count - 2; // Minus two because array index starts at 0 and also we want the second to last occurence

$i = 0;
$output = "";
foreach ($url_explode as $portion){

    $output.=$portion;

    if ($i == $affected_portion){
        $output.= "#";
    }

    $i++;

}

$new_url = $output;

In my case this solved my problem:

$url = $this->Link();
$url = rtrim($url, '/');
$url = substr_replace($url, '#', strrpos($url, '/') + 1, 0);

Assuming you now have

$url = $this->Link(); // e.g. /foo/bar/my-urlsegment

You can combine it like

$handledUrl = $this->ParentID 
    ? $this->Parent()->Link() + '#' + $this->URLSegment
    : $this->Link();

where $this->Parent()->Link() is e.g. /foo/bar and $this->URLSegment is my-urlsegment

$this->ParentID also checks if we have a parent page or are on the top level of SiteTree

I might be tooooo late for answering this question but I thought this might help you. You can simply use preg_replace like as

$url = '/foo/bar/url/';
echo preg_replace('~(\/)(\w+)\/$~',"$1#$2",$url);

Output:

/foo/bar/#url