PHP how to remove and add commas

How can I remove extra commas and add commas for example using PHP

user submitted data

stack,,,,,,,,,,,,,,overflow

should output.

stack, 开发者_C百科overflow

$out = preg_replace("/,+/",", ",$in);

preg_replace('/[,]+/', ',', $string); should do it... though depending on the nature of the input you may need a more complex expression.

$str = preg_replace('/,+/' , ',' , $str);

This will replace each sequence of one or more commas with one comma.