base64_decode()

(PHP 4, PHP 5, PHP 7)

对使用 MIME base64 编码的数据进行解码

说明

对 base64 编码的$data进行解码。

参数

编码过的数据。

当设置$strict为TRUE时，一旦输入的数据超出了 base64 字母表，将返回FALSE。否则会静默丢弃无效的字符。

返回值

返回原始数据，或者在失败时返回FALSE。返回的数据可能是二进制的。

更新日志

范例

Example #1base64_decode()示例

以上例程会输出：

This is an encoded string

参见

• base64_encode() 使用 MIME base64 对数据进行编码
• » RFC 2045的 6.8 章节。

If you want to save data that is derived from a Javascript canvas.toDataURL() function, you have to convert blanks into plusses. If you do not do that, the decoded data is corrupted: 

I had some trouble trying to let base64_decode decode base64-strings longer than ~5k chars.
The base64-decoding function is a homomorphism between modulo 4 and modulo 3-length segmented strings. That motivates a divide and conquer approach: Split the encoded string into substrings counting modulo 4 chars, then decode each substring and concatenate all of them.
Then instead of 

for big $encoded strings, it's saver to use

where 256 can be replaced by a sufficiently small modulo 4 natural.

This function supports "base64url" as described in Section 5 of RFC 4648, "Base 64 Encoding with URL and Filename Safe Alphabet" 

Base64 for URL parameters/filenames, that adhere to RFC 4648.
Defaults to dropping the padding on encode since it's not required for decoding, and keeps the URL free of % encodings.

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