来自 php 的 echo char(128) 及以上不起作用 [英] echo char(128) and above from php does not work

问题描述

我有一个响应两个字符的服务器端 process.php 脚本:

I have a server side process.php script that echos two chars:

echo chr(127);
echo chr(128);

在客户端，我有一个 java 脚本(在 UTF-8 编码的 html 页面中运行)，它发布到 php 脚本并期待响应:

On the client side, I have a java script (running in an html page with UTF-8 encoding) that posts to the php script and expects a response:

const xhr = new XMLHttpRequest();
// post xhr to php, check for DONE and 200, and get the response
console.log(xhr.responseText);       

对于 127，我得到的响应是一个字符串，正如预期的那样，其中一个字符代表 127.但是对于 128 及以上，它给了我 3 个字符，-17、-65 -67.梳理并拖网，但一无所获.很惊讶没有在网上找到任何关于从服务器到客户端传输字节的信息.我是桌面 C++ 程序员，顺便说一句，这让我难住了！

For 127, I get the response as a string with one character representing 127 as expected. But for 128 and above it gives me 3 chars, -17, -65 -67. Combed and trawled the net, but nothing. Am quite surprised to not find any info online on transmitting bytes from a server to a client. Am a desktop C++ programmer, btw hence this has me stumped!

推荐答案

因为您正在发送字节，所以您需要停止考虑文本和字符.JavaScript 在内部是 UTF-16，您将通过 HTTP 从 PHP 传输文本，PHP 可以设置自己的编码.

Because you are sending bytes, you need to stop thinking about text and characters. JavaScript is UTF-16 internally, and you'll be transporting text across HTTP from PHP which gets to set it's own encoding.

如果你想解析原始字节 在 JavaScript 中，您需要查看 数组缓冲区.收到数据后，您可以编写一个 DataView 在它上面并抓取字节.如果您只是 8 位，则也不用担心字节顺序.

If you want to parse raw bytes in JavaScript, you'll want to look into the ArrayBuffer. Once you receive your data, you can compose a DataView over it and grab the bytes. If you are 8-bit only, you shouldn't need to worry about endianness, either.

        const xhr = new XMLHttpRequest();
        xhr
            .addEventListener(
                'load',
                () => {
                    const buffer = xhr.response;
                    const view = new DataView( buffer );
                    const byte = view.getUint8( 0 );
                    console.dir( byte );
                }
            );
        xhr.open( 'GET', '/my/end-point' );
        xhr.responseType = 'arraybuffer';
        xhr.send();

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