Returning only 0-9 and dashes from string

Question

I would like to take a string, and strip any characters apart from 0-9 and - (dashes).

Example:

if I have a string that looks like:

10-abc20-30

How can I make this string return

10-20-30

(Strip all characters besides numbers and dashes)

Is there some kind of regex to use within preg_match or str_replace ?

Answer 1

$result = preg_replace('/[^\d-]+/', '', $subject);

[^\d-] matches any character except digits or dash; the + says "one or more" of those, so adjacent characters will be replaced at once.