Remove empty lines from string, but allow one empty between every line

Question

I would like to remove excessive empty lines from a string, but allow one empty line between every line. Like: ``` line1 line2 ``` Should become: ``` line1 line2 ``` I did find the following regex (forgot where i found it): ``` preg_replace('/^
+|^[	\s]*
+/m','',$message); ``` This works, but removes all empty lines without leaving an empty line between every line. Edit: I just created a quick example at http://jsfiddle.net/RAqSS/

Accepted Answer

Try replacing:

```

(\s*
){2,}
```

with:

```

Like this:

```
preg_replace('/
(\s*
){2,}/', "

", $message); // Quotes are important here.
```

If you don't want an empty line, you would change the `{2,}` to a `+` and use a single `
`. It would actually work with a `+` instead of `{2,}`. The `{2,}` is an optimization.

Remove empty lines from string, but allow one empty between every line

Solution

Problem