use of %s

Hi, new to PHP - have read half of the WROX book, but didn't find an explanation of the use of %s and %d as placeholders, as in the following code.

printf("Untrusted PHP code: <i>%s</i>",
htmlspecialchars($data));

why this syntax, instead of

printf("Untrusted PHP code: <i>htmlspecialchars($data)</i>",
);

Is there somewhere an explanation of using %s and %d as placeholders?

Thanks for any help on this.

------------------
John Newsom
Director of Instructional Technology
Bellevue Schools, Washington State

The %s and %d are C string format specifiers. You can find them in any C or C++ book.

Go to www.php.net/manual and have fun searching for print, echo, printf, sprintf.

Nelson