sodium_crypto_secretstream_xchacha20poly1305_init_push

<?php
function encrypt_file(string $inputFilePath, string $outputFilePath, string $key): void
{
    [$state, $header] = sodium_crypto_secretstream_xchacha20poly1305_init_push($key);

    $inputFile = fopen($inputFilePath, 'rb');
    $outputFile = fopen($outputFilePath, 'wb');
    // Write the header:
    fwrite($outputFile, $header);
    $inputFileSize = fstat($inputFile)['size'];

    // Encrypt the file and write its contents to the output file:
    for ($i = 0; $i < $inputFileSize; $i += 8175) {
        $ptxt_chunk = fread($inputFile, 8175);
        $ctxt_chunk = sodium_crypto_secretstream_xchacha20poly1305_push($state, $ptxt_chunk);
        fwrite($outputFile, $ctxt_chunk);
    }

    sodium_memzero($state);
    fclose($inputFile);
    fclose($outputFile);
}

// sodium_crypto_secretstream_xchacha20poly1305_keygen()
$key = sodium_base642bin('MS0lzb7HC+thY6jY01pkTE/cwsQxnRq0/2L1eL4Hxn8=', SODIUM_BASE64_VARIANT_ORIGINAL);

file_put_contents('hello.txt', 'Hello world!');
encrypt_file('hello.txt', 'hello.txt.encrypted', $key);
var_dump(sodium_bin2hex(file_get_contents('hello.txt.encrypted')));
?>