Converting regional decimal numbers

Hello all, I have a few users that use a different number format, other than the US one, which is 1.526,23 . That is, the comma is used as a separator for the fractional part of the number (.23) and the dot is used to separate thousands. Therefore, I need to convert 1.526,23 to 1,526.23, invert the comma and the dot. Some numbers are formated correctly so nothing needs to be done, while other need that. I have writen a function to perform that but it reads char by char and has test cases. I first check the position of the dot and the comma. It one is higher than the other than I need to convert, if not than I do nothing. I would like to make it simpler and more efficent and for that I need some help from some of the PHP regex experts. Can anyone help me with this matter? Thanks in advance.