I need a function which searches a dir for UP TO 5 files (only MAX 5 files in the dir). The files have the same names almost, an ID nr ending with `'_1'` for `file` 1, `'_2'` for `file 2` etc. It simply ends with a underscore, and then the file-nr. Example:

```
   filename = id.'_1.jpg'; // File 1.

```

Here is the tricky part, read carefully: Now I need to search this dir and if there is (for example) `a file1, and file3, BUT NO file2, then rename file3 to file2.`

In other words, I need to find 'gaps' between the names and rename all files so they come in order, without 'gaps'.

So another example, if dir contains 3 files ending with `'_1.jpg' and '_3.jpg' and '_4.jpg'` I want it to rename the files so that they are `'_1.jpg' and '_2.jpg' and '_3.jpg'`, they come in order...

As I said there is max 5 files in this folder.

Please help me out... I am not that good in writing functions in PHP... 
Thanks

PS: If I'm not clear, let me know and I will put in some more examples...