stripping out all characters from a string, leaving numbers

Question

Hay, i have a string like this:

v8gn5.8gnr4nggb58gng.g95h58g.n48fn49t.t8t8t57

I want to strip out all the characters leaving just numbers (

Answer 1

$str = preg_replace('/[^0-9.]+/', '', $str);

replace substrings that do not consist of digits or . with nothing.