为什么这个 base64 字符串不解码？

Question

我的代码：

<?php
$a = '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';
echo strlen(base64_decode($a)) . "nn";
echo strlen(sodium_base642bin($a, SODIUM_BASE64_VARIANT_ORIGINAL_NO_PADDING));

base64_decode可以很好地解码该字符串，但sodium_base642bin失败，无论$id参数是什么(SODIUM_BASE64_VARIANT_ORIGINAL、SODIUM-BASE64.VARIANT_ORIGINAL_NO_PADDING、SODIUM_BASE64_ARIANT_URLSAFE和SODIUM_BASE64_VARIANT_URL SAFE_NO_PADING(。更具体地说，sodium_base642bin抛出以下(无用的(异常：

Fatal error: Uncaught SodiumException: sodium_base642bin(): Argument #1 ($string) must be a valid base64 string

有什么想法吗？

Answer 1

正如@Rylee在评论中所说，您的base64字符串格式不正确。由于默认情况下base64_decode会通过在非严格模式下工作来忽略一些错误，因此它不会失败。但通过将strict参数设置为true，函数将返回false。

要检查出了什么问题，你可以使用像这个base64验证器这样的工具，它会说它无效，甚至建议你修复它

修复后，如果将结果与编码字符串逐字符进行比较，就会发现必须删除最后一个字符S才能获得完全有效的base64编码字符串。