Returns true if and only if $value is a valid ISBN.
| Parameters: | string – |
|---|---|
| Return type: | bool |
Set separator characters.
It is allowed only empty string, hyphen and space.
| Parameters: | string – |
|---|---|
| Throws ExceptionInvalidArgumentException: | |
| When $separator is not valid | |
| Return type: | Isbn Provides a fluent interface |