sprintf参数交换和HEREDOC

Question

我正试图以这种方式在heredoc上使用sprintf。它不会工作。知道如何解决这个问题吗？

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

$year = '2013';

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

echo $i;

Notice: Undefined variable: s in

Answer 1

因为HEREDOC就像一个双引号字符串，PHP试图将$s插入为变量。请尝试使用NOWDOC

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

Answer 2

或者只是逃避美元符号：

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

这很有用，例如在PHP 5.2中没有nowdoc语法。