File contents and memory

json-base64.php

<?php

$app->get('/', function () {

    // Write some data to a temp file
    $stream = fopen('php://temp', 'w+');
    for ($i = 0; $i != 100000; $i++) {
        fwrite($stream, str_repeat(strval($i), 100) . PHP_EOL);
    }
    
    // Go to the start
    rewind($stream);

    return response()->json([
        'file' => base64_encode(stream_get_contents($stream))
    ]);
});

stream.php

<?php

use Symfony\Component\HttpFoundation\StreamedResponse;

$app->get('/', function () {

    // Write some data to a temp file
    $stream = fopen('php://temp', 'w+');
    for ($i = 0; $i != 100000; $i++) {
        fwrite($stream, str_repeat(strval($i), 100) . PHP_EOL);
    }
    
    // Go to the start
    rewind($stream);

    return new StreamedResponse(function () use ($stream) {
        fpassthru($stream);
    }, 200, [
        'Content-Type' => 'text/plain',
        'Content-disposition' => 'attachment; filename="example.txt"',
    ]);
});