printf() in a variable, or alternative to

I need to be able to format data.

Printf() is perfect because I need a certain amount of characters (30
for address).

However I need this formatted data to be inside a file that's fwrite()
and then FTPed to a distributor who will parse it and input into their
database.


printf("% 4d",$orderID[0]); does not work in

$thisContent="

"data" .
"moredate" .
"evenmoredata" .

";


In effect I need the output of printf() to be placed inside a variable
and I don't see how to do that. Str_pad(), of course, does not work.

Thx for any hints.

mayo