sprintf argument swapping and HEREDOC

Question

I'm trying to use sprintf on a heredoc this way. It wont work. Any idea how to solve this?

$i = <<<EOD
This is your invoice for %1$s %1$s %1$s %1$s
EOD;

$year = '2013';

$i = sprintf($i,$year);

echo $i;

Notice: Undefined variable: s in

Answer 1

Because HEREDOC acts like a double-quoted string, PHP is attempting to interpolate the $s as a variable. Try NOWDOC instead

$i = <<<'EOD'
This is your invoice for %1$s %1$s %1$s %1$s
EOD;

Answer 2

Or just escape the dollar signs:

$i = <<<EOD
This is your invoice for %1\$s %1\$s %1\$s %1\$s
EOD;

This is useful e.g. in PHP 5.2 where there's no nowdoc syntax.