PHP replace all dots to comma [duplicate]

Question

I have string

10.2, 200.3, 33.00

and I want it to be replaced as

10,2, 200,3, 33,00

I tried

preg_replace("/[.]$/","/\d[,]$/",$input);

but it is not replacing!

I can't use str_replace because it's task in university

Answer 1

Do not use regular expresion when dumb str_replace() suffices:

$str = str_replace('.', ',', $str)

See docs: http://php.net/str_replace