PHP & “Data” URL scheme（转）

基本上所有的对文件操作的API, 都迁移到的了PHP stream上, 所以, 绝大部分对文件操作的API都是支持Data URL的.

当某个API需要操作对象是文件的时候, 我们其实是可以采用Data URL让他接受一个文件内容字符串的.

比如在#62961中, 请求PHP提供一个exif_imagetypefromstring API, 因为目前的exif_imagetype API只接受文件名, 而提出者已经得到了文件内容在内存中, 不希望只能通过写到一个临时文件, 然后再调用exif_imagetype .

1. <?php
2. //we already have $bindata
3. $tmpfile = tempnam('/tmp', 'upload');
4. file_put_contents($tmpfile, $bin_data);
5. $extension = image_type_to_extension(exif_imagetype($tmpfile));
6. unlink($tmpfile);

那么, 这个时候, 我们就可以借助Data URL了:

1. <?php
2. //we already have $bindata
3. $base64_data = base64_encode($bin_data);
4. $extension =
5. image_type_to_extension(exif_imagetype("data://image/;base64," . $base64_data ));

另外, Data URL还有一个比较常见的使用场景, 比如下面这个图:
aaarticlea/png;base64,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" alt="Yaf logo" />

源码就是：

<img src="data:image/png;base64,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" />