Outputting file contents as binary as AJAX response - php

Question

OK the title doesn't give much a way so let me explain my very strange set-up.
Two servers are involved:
website: remote
localhost: local machine
The workflow is as follows:
The site calls localhost via cross-domain AJAX
In response localhost dynamically creates a ZIP file via PHP's ZipArchive lib
localhost conveys the raw data that comprises the archive as the AJAX response
The request is made and the archive is made - all good. The archive is openable, all good. What I'm stuck on now is how to convey that archive as the AJAX response, such that it can be "put together again" (à la Humpty Dumpty). When I do this currently (via file_put_contents()) it errors on opening, saying it's invalid. Currently I'm just outputting the archive's raw data:
echo file_get_contents('path/to/archive.zip');
This is fine, but sends garbled characters in the response. I don't know much about encoding and headers, so apologise if this seems obvious.
For the response, should I be looking to convert it to binary, or sending certain headers etc? I tried sending the multipart/form-data header, but no dice. Headers aren't my strong point.
Please note cURL is not an option in this scenario, else I'd be laughing.

Answer 1

You have to read the zip file as a binary data with Blob javascript class.
This is a code snippet from Mozilla documentation
var oReq = new XMLHttpRequest();
oReq.open("GET", "/myfile.png", true);
oReq.responseType = "arraybuffer";
oReq.onload = function(oEvent) {
var blob = new Blob([oReq.response], {type: "application/octet-stream"}); //
// you have nothing to do with the blob...
// ...
};
oReq.send();
Then send this file (blob) with POST method to your destination
var oReq = new XMLHttpRequest();
oReq.open("POST", url, true);
oReq.onload = function (oEvent) {
// Uploaded.
};
oReq.send(blob); //the blob that you loaded
you can read more in the documentation by Mozilla :https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Sending_and_Receiving_Binary_Data