regular expression to match an empty (or all whitespace) string

Question

i want to match a string that can have any type of whitespace chars (specifically I am using PHP). or any way to tell if a string is empty or just has whitespace will also help!

Accepted Answer

You don't need regular expressions for that, just use:

```
if ( Trim ( $str ) === '' ) echo 'empty string';
```

regular expression to match an empty (or all whitespace) string

Solution

Problem