sprintf using the same values multiple times

Question

I'm trying to use the same value in different places when using sprintf, but failing.

<?php

$score = 50;
$percent = 10;

$str = "Hello: You scored %s (%s%%). Your score is %2$s %%"; //Problem is here %2$s

echo sprintf($str,$score,$percent);
?>

I get this error: Notice: Undefined variable: s in C:\web\apache\htdocs\sprintf.php on line 6 Warning: sprintf(): Too few arguments in C:\web\apache\htdocs\sprintf.php on line 8

Answer 1

Use single quotes instead of double quotes:

$str = 'Hello: You scored %s (%s%%). Your score is %2$s %%';

Variables are expanded inside double quotes, so $s was treated as a variable, not a formatting option.

If you want to use double quotes, you can escape the dollar sign:

$str = "Hello: You scored %s (%s%%). Your score is %2\$s %%";

Answer 2

A $ inside of double quoted strings is used for variable interpolation, PHP is looking for the variable $s here. Use single quoted strings and number all your arguments while you're at it:

'Hello: You scored %1$s (%1$s%%). Your score is %2$s %%'