PHP - 用二进制数据打包数组

Question

有一个服务（php）将图像发送到客户端（php）。header('Content-Type: image/png');readfile($image);如果不仅需要发送图像，还需要发送一些数据，该怎么办。$arrayToSend = [    'image' => file_get_contents($image),    'some_data' => [        'a' => 1,        'b' => 2    ]];服务如何打包 $arrayToSend 以便客户端可以解包？不将图像转换为 base64（因为尺寸太大）。

Answer 1

如果您通过 HTTP 通信，@Danon 的标头方法可能是要走的路，但其他传输可能不支持发送额外的标头，因此您需要将它们与二进制数据一起打包，然后在接收端解包。

<?php

class Codec

{

    /**

     * Pack metadata along with binary data

     *

     * @param $meta

     * @param $data

     * @return false|string

     */

    public static function encode($meta, $data)

    {

        $meta = base64_encode($meta);

        //determine length of metadata

        $metaLength = strlen($meta);

        //The first part of the message is the metadata length

        $output = pack('VA*', $metaLength, $meta);

        //Length and metadata are set, now include the binary data

        $output .= $data;

        return $output;

    }

    /**

     * Unpack data encoded via the encode function.

     * Returns an array with "meta" and "data" elaments

     *

     * @param $content

     * @return array

     */

    public static function decode($content)

    {

        //Get the length of the metadata content

        $metaLength = unpack('V', $content)[1];

        //Slice out the metatdata, offset 4 to account for the length bytes

        $metaPacked = substr($content, 4, $metaLength);

        //Unpack and base64 decode the metadata

        $meta = unpack('A*', $metaPacked)[1];

        $meta = base64_decode($meta);

        //The binary data is everything after the metadata

        $data = substr($content, $metaLength+4);

        return [

            'meta' => $meta,

            'data' => $data

        ];

    }

}

//Load contents of a binary file

$imageFilePath = 'path_to_image.png';

$data = file_get_contents($imageFilePath);

//Arbitrary metadata - could be anything, let's use JSON

$meta = [

    'filename' => 'foo.png',

    'uid' => 12345,

    'md5' => md5_file($imageFilePath)

];

$metaJson = json_encode($meta);

//Encode the message, you can then send this to the receiver

$payload = Codec::encode($metaJson, $data);

//Receiver decodes the message

$result = Codec::decode($payload);

//Decode our JSON string

$resultMeta = json_decode($result['meta'], true);

echo 'Filename: '.$resultMeta['filename'].PHP_EOL;

echo 'UID: '.$resultMeta['uid'].PHP_EOL;

//We included an MD5 hash of the file, so we can verify here

if($resultMeta['md5'] != md5($result['data']))

{

    echo 'MD5 mismatch!';

}