Return only 0-9 and dashes from string

Question

I would like to take a string and delete any characters except 0-9 and - (dash).

Example:

if I have a line that looks like this:

10-abc20-30

How can I return this line

10-20-30

(separate all characters except numbers and dashes)

Is there any regular expression to use in preg_match or str_replace?

Answer 1

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

[^\d-] matches any character except digits or dashes; + says "one or more" of them, so adjacent characters will be replaced immediately.

Answer 2

Assuming your data is in $ string, this will delete all characters except dashes and numbers

 $string = preg_replace('/[^-0-9]/', null, $string);