Why doesn't sprintf() output anything?

Question

I've never used these functions before but after reading a lot about sprintf(), I decided I should get to know it.

So I went ahead and did the following.

function currentDateTime() {
  list($micro, $Unixtime) = explode(" ",microtime());
  $sec= $micro + date("s", $Unixtime);
  $sec = mb_ereg_replace(sprintf('%d', $sec), "", ($micro + date("s", $Unixtime)));
  return date("Y-m-d H:i:s", $Unixtime).$sec;
}

sprintf(currentDateTime());

It prints nothing. Using the printf() function on the other hand:

printf(currentDateTime());

It prints the result just fine. So what's the difference between these 2 functions and how do I properly use the sprintf() function?

score 59 · Accepted Answer · answered Jun 20 '09 at 14:40

59

sprintf() returns a string, printf() displays it.

The following two are equal:

printf(currentDateTime());
print sprintf(currentDateTime());

answered Jun 20 '09 at 14:40

molf

71,048
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24

I remember it by thinking '**silent** `printf()`' :) – deed02392 Mar 30 '12 at 16:41
@deed02392, Isn't that `s` representing "string"? – Pacerier Dec 26 '14 at 03:50
No, because `printf()` outputs a string too. – mickmackusa Apr 08 '22 at 03:15

score 14 · Answer 2 · answered Jun 20 '09 at 14:40

14

sprintf() prints the result to a string. printf() prints it to standard output ie:

printf(currentDateTime());

is equivalent to:

echo sprintf(currentDateTime());

answered Jun 20 '09 at 14:40

cletus

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score 6 · Answer 3 · answered Jun 20 '09 at 14:44

sprintf() returns a string while printf() outputs a string. So you'd have to do something like the following:

function currentDateTime() {
  list($micro, $Unixtime) = explode(" ",microtime());
  $sec= $micro + date("s", $Unixtime);
  $sec = mb_ereg_replace(sprintf('%d', $sec), "", ($micro + date("s", $Unixtime)));
  return date("Y-m-d H:i:s", $Unixtime).$sec;
}

$output = sprintf(currentDateTime());
printf($output);

http://www.php.net/sprintf

http://www.php.net/printf

Why doesn't sprintf() output anything?

3 Answers3

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