Lets say I have:

```
_Example
_1979

```

How do we know if the character after `_` is a `number` or a `letter`? I am not familiar with `regex`.

This is what I am doing to only find strings starting with `_` and then I am removing the `_` as I am only using it for other reasons:

```
if (strpos($txt, '_') !== false) {
   $output = str_replace('_', ' ', $txt);
   echo $output;
  ...Now I should find if the first `character` is a `letter` or a `number`

```