PHP sprintf的用法

Question

实例一:这是正确的

<?php
$num = 5;
$location = 'tree';
$format = 'The %2$s contains %1$d monkeys';
echo sprintf($format, $num, $location)
?>

实例二:为什么这是错误的

<?php
$num = 5;
$location = 'tree';
$format = "The %2$s contains %1$d monkeys";
echo sprintf($format, $num, $location)
?>

Answer 1

例二中双引号中需要转义 $format = "The %2\$s contains %1\$d monkeys";

Answer 2

把$符转义即可 "The %2\$s contains %1\$d monkeys"