```
/^([a-z]:)?\//i

```

I don't quite understand what the `?` in this regex if I had to explain it from what I understood:

Match begin "Group1 is a to z and :" outside `?` (which I don't get what its doing) `\/` which makes it match `/` and option `/i` "case insensitive".

I realize that this will return 0 or 1 not quiet sure why because of the `?`

Is this to match directory path or something ?

If I test it:

`$var = 'test'` would get 0 while `$var ='/test';` would get 1 but `$var = 'test/'` gets 0

So anything that begins with `/` will get 1 and anything else 0.

Can someone explain this regex in elementary terms to me?