Convert phone number format to plain number

Question

I have some phone formatted variable like these variables:

$phone1 = "(123) 123-1234";
$phone2 = "+1234567892";
$phone3 = "123-434-3432

How can I convert these variables to plain number in php ?

the results should be like these variables:

$new_phone1 = "1231231234";
$new_phone2 = "1234567892";
$new_phone3 = "1234343432";

Answer 1

Use preg_replace which uses regex!

preg_replace("/[^0-9]/","",'123-434-3432');

Removes everything but numbers!