Remove Commas from Numbers and Leave Commas between Words

Dear forum,
I need to remove commas from numbers and leave commas between words, but I can’t find regular expression that does this. Numbers are always same without whitespace characters, but text can be different (with whitespace characters on both side, on left, on right side of comma, or without white spaces) like:
one,two
tree , four
five, six
seven ,eight
Can please somebody help me with this.

preg_replace(‘@(\d),(\d)@’, ‘$1$2’, $string);

Can you please explain the preg_replace function or give the link to tutorial

Regular Expressions (or a regex as a single one might be known) is perhaps best thought of another language you have to learn (yes, another one) a bit like SQL is not part of PHP, but you end up learning it.

preg_replace() is merely a wrapper around a particular family of regexes.

With my oversimplified explanation in mind the terms [google]regex tutorial[/google] should get you going.