Stripping whitespace between commas?

[Boofo]

Does anyone know how I can make the following pre_replace also strips out whitespace BETWEEN the commas?

Right now it will trim the elements of any whitespace that may come before or after the comma. But, say, I have this:

2    4  ,    3        ,    1      1

It won't strip out the space between the 2 and the 4, or the 1 and the 1.

$str = trim(preg_replace('|\\s*(?:' . preg_quote($delimiter) . ')\\s*|', $delimiter, $str));