PHP printf adds something after formatted string

Question

When im using printf,

printf("%.2f z?", 20.4);

it returns

20.40 z?9

but i want

20.40 z?

When i use sprintf("%.2f z?", 20.4) there is no problem.

z? is polish currency symbol. When i replace "?" with "l" i still have problem like this, so it looks like this is not related with encoding.

How can I use printf for currency correctly?

Answer 1

I got it.

I wrote:

echo printf(...);

instead of just:

printf(...);

After string produced by printf() i got that string length, which is value returned by printf (in fact - added number was 9 in case of 123.45 value, in 20.4 case it was number 8).