Stream data from OpenAI's API using AJAX, PHP, and server-sent events

Question

How to use Server Sent Events (SSE) to stream data from the above API to a browser client using JavaScript and PHP? I've been working on this problem for hours and I can't seem to figure out what's going wrong. For reference, I tried adapting the solution here: Stream DATA From openai GPT-3 API using PHP

The rest of my code is more or less the same as in the question above. The only part I modified that didn't work was:

curl_setopt($ch, CURLOPT_WRITEFUNCTION, function ($curl, $data) {
        # str_repeat(' ',1024*8) is needed to fill the buffer and will make streaming the data possible
        $data = json_decode($data, true);

        $text = $data['choices'][0]['text'];

        echo $text . str_repeat(' ', 1024 * 8);
        return strlen($data);
    });

First, I tried returning only the "text" property from the "choices" array (see sample API response below).

This is the response I received:

Note: Trying to access array offset on value of type null in C:FILE_PATHsse.php.

Secondly, how to transfer "text" to an element on the client in real time? This is my implementation so far.

JavaScript

$.ajax({
          type: "POST",
          url: "sse.php",
          data: JSON.stringify({
            prompt: "What is the best way to",
            num_completions: 1,
            temperature: 0.5,
          }),
          contentType: "application/json",
          success: function (response) {
            const source = new EventSource("sse.php");

            source.onmessage = function (event) {
              const div = document.getElementById("response");
              div.innerHTML += event.data + "<br>";
              console.log(event);
            };
          },
        });

A sample chunk of data streamed by the API is shown below. I'm trying to stream only the "text" portion back to the browser.

data: {"id": "cmpl-XXXXXXXXXXXXXXXXXXXXXXX", "object": "text_completion", "created": 1671700494, "choices": [{"text": " Best", "index": 0, "logprobs": null, "finish_reason": null}], "model": "text-davinci-003"}

data: {"id": "cmpl-XXXXXXXXXXXXXXXXXXXXXXX", "object": "text_completion", "created": 1671700494, "choices": [{"text": " way", "index": 0, "logprobs": null, "finish_reason": null}], "model": "text-davinci-003"}

data: {"id": "cmpl-XXXXXXXXXXXXXXXXXXXXXXX", "object": "text_completion", "created": 1671700494, "choices": [{"text": " to", "index": 0, "logprobs": null, "finish_reason": null}], "model": "text-davinci-003"}

data: [DONE]

How should I implement this? I'm at my wits' end. Thanks in advance.

Answer 1

I found the solution using the following code:

//Placed at the beginning of the script
@ini_set('zlib.output_compression', 0);
ob_implicit_flush(true);
ob_end_flush();

header("Content-Type: text/event-stream");
header("Cache-Control: no-cache");

//Initialize cURL and set the necessary headers and request parameters
...
...
curl_setopt($curl, CURLOPT_WRITEFUNCTION, function ($curl, $data) {
    echo $data;
    return strlen($data);
});

$curl_response = curl_exec($curl);

echo $curl_response;

I then use JavaScript to extract the text like this:

source.onmessage = function (event) {
  const div = document.getElementById("response");
  text = JSON.parse(event.data).choices[0].text;
  div.innerHTML += text;
};