Copy folder tree-recursively with depth control

I want to copy a whole folders/files tree from one location to another, but for a particular depth I want to perform a transliteration of the destination folder from one language to another.

So for /src/depth1/depth2/depth3/depth4/file I want to transliterate all depth3 folders to another language before copying them over to the destination path.

So I found this little, robust recursive function, which should help me in my task, and then I tried to add a depth control feature so that the transliteration replacement takes place only on depth3 folders. But at first, what I did only added to the depth. Then I thought I found the correct place to add the $depth--;, but unfortunately I can’t figure out where to subtract from it in order to start over a new branch…

Could someone help figure this out please?

recurse_copy('TOCOPY/', 'TEST/');

function recurse_copy($src,$dst,$depth = 0) { 
    echo $src . ' ' . $depth.'<br>';
    $dir = opendir($src); 
    @mkdir($dst); 
    while(false !== ( $file = readdir($dir)) ) { 
        $depth++;
        if (( $file != '.' ) && ( $file != '..' )) { 
            if ( is_dir($src . '/' . $file) ) { 
                recurse_copy($src . '/' . $file,$dst . '/' . $file, $depth); 
            } else { 
                $depth--;
              //  copy($src . '/' . $file,$dst . '/' . $file); //I commented this line to save time from copying files again and again while I'm experimenting with the depth control...
            } 
        } 
       
    } 
    closedir($dir); 
}

Answer

Not tested, but if my understanding is right this should work, plus minus 1 depth.

recurse_copy('TOCOPY/', 'TEST/', 3);

function recurse_copy($src, $dst, $depth = 0) { 
    echo $src . ' ' . $depth . '<br>';
    if ($depth <= 0) {
      return;
    }
    $dir = opendir($src); 
    @mkdir($dst); 
    while(false !== ( $file = readdir($dir)) ) { 
        if (( $file != '.' ) && ( $file != '..' )) { 
            if ( is_dir($src . '/' . $file) ) { 
                recurse_copy($src . '/' . $file,$dst . '/' . $file, $depth - 1); 
            } else { 
              //  copy($src . '/' . $file,$dst . '/' . $file); //I commented this line to save time from copying files again and again while I'm experimenting with the depth control...
            } 
        } 
       
    } 
    closedir($dir); 
}

Addition: This version will rename some directories according to their depth.

recurse_copy_special('TOCOPY/', 'TEST/');

function recurse_copy_special($src, $dst, $depth = 0)
{
    echo $src . ' ' . $depth . '<br>';
    $base = basename($dst);
    $dir = dirname($dst);
    
    if ($depth == 1) {
        $dst = $dir . '/' . 'changed1-' . $base;
    }
    if ($depth == 2) {
        $dst = $dir . '/' . 'changed2-' . $base;
    }
    if ($depth == 3) {
        $dst = $dir . '/' . 'changed3-' . $base;
    }
    $dir = opendir($src);
    if (!file_exists($dst)) {
        mkdir($dst);
    }
    while (false !== ($file = readdir($dir))) {
        if (($file != '.') && ($file != '..')) {
            if (is_dir($src . '/' . $file)) {
                recurse_copy_special($src . '/' . $file, $dst . '/' . $file, $depth + 1);
            } else {
                copy($src . '/' . $file, $dst . '/' . $file);
            }
        }

    }
    closedir($dir);
}