How to add a subdirectory before the last slash to the url?

Question

PHP

We have a URL like
site.ru/subdir1/subdir2/subdirN/filename.jpg
How can I add another directory with a specific name before /filename.jpg using php and regular expressions.
The output should be the line
site.ru/subdir1/subdir2/subdirN /newsubdir /filename.jpg

Answer 1

dirname($path).'/'.$dir.'/'.basename($path)

Answer 2

Try something like this.
I don’t have php at hand, I can’t check whether it is necessary to escape the normal slash in the second argument.

url=preg_replace("/(\w+)\/(w+.jpg)/i", "\$1/newsubdir/\$2", $url);