JSON Generator Parser

A PHP library for event-driven recursion free SAX-style JSON parser fed by generator.

Rationale

Provide a JSON parser with lenient rules that accepts input from an LLM stream.

There are cases where you need a structured LLM response, but want to display output to the user as soon as there are token stream available. This library provides a listener interface, that is called as JSON is parsed.

As LLM's may generate a bit wonky JSON, this library has a non-strict option that permits various JSON errors, which wouldn't change the semantic meaning of the response.

Requirements

• PHP >=8.2

Installation

This library is available on Packagist.

composer require sop/json-generator-parser

Example

Here we receive a stream from LLM HTTP API. We assume that stream is already processed such that $lines generator yields logical SSE lines.

$lines = ... // Generator that produces lines from HTTP SSE stream
$input = (function (Generator $lines): Generator {
    foreach ($lines as $line) {
        // Just an example, no error checking nor validation
        if (!str_starts_with($line, 'data:')) {
            continue;
        }
        $json = trim(substr($line, 5));
        $data = json_decode($json);
        // Yield content delta chunks
        if (!empty($data->choices[0]->delta->content)) {
            yield $data->choices[0]->delta->content;
        }
    }
})($lines);
$listener = new CallbackJSONListener(
    function (array $keys, mixed $value): void {
        // Here you can handle parsed values.
        // Keys contain all structural indices leading to the value.
        // eg. for `{"a":["x","y","z"]}` JSON the second array value would
        // have keys ["a", 1] and value "y"
    }
);
$parser = new JSONGeneratorParser($listener, false);
$parser->parse($input, true);

License

This project is licensed under the MIT License.