为什么不能使用字符串编号作为会话变量中的索引？
why can't you use a string number as a index in the session variable?
示例：
$_SESSION['10'] = 'testing';
echo $_SESSION['10'];
上面不会打印出任何东西...我发现（经过长时间的挫折）你不能使用字符串数字作为 $_SESSION 变量的索引。有人知道为什么吗？
引自here：
The PHP session storage mechanism was originally built around
"registering" variables, so the keys in $_SESSION must be names that
could be treated as variables in their own right.
This means that $_SESSION[10] is invalid, because </code> wouldn't be
a valid variable name, and since <code>$foo[10] and $foo['10'] refer to
the same thing, $_SESSION['10'] is invalid as well.
示例：
$_SESSION['10'] = 'testing';
echo $_SESSION['10'];
上面不会打印出任何东西...我发现（经过长时间的挫折）你不能使用字符串数字作为 $_SESSION 变量的索引。有人知道为什么吗？
引自here：
The PHP session storage mechanism was originally built around "registering" variables, so the keys in
$_SESSIONmust be names that could be treated as variables in their own right. This means that$_SESSION[10]is invalid, because</code> wouldn't be a valid variable name, and since <code>$foo[10]and$foo['10']refer to the same thing,$_SESSION['10']is invalid as well.