PHP Streaming very large video (> 4GB) problem

I am trying to play a long video (4gb+) using an 8 MB chunk but it is not working. everything looks good with video until 2 GB size but getting problem for very large video size. Is anything I will need to optimize at PHP, Apache side, or anything needed to update in following script to support very large video?

<?php
require 'awss3/vendor/autoload.php';
use Aws\S3\S3Client;  
use Aws\Exception\AwsException;

$objectkey = '<VIDEO>.mp4'; 

$buffer = '';
$bucketname = '<BUCKETNAME>';
$key = '<KEY>';
$secret = '<SECRET_KEY>';
$region = '<REGION>';

$s3 = new S3Client([
    'region' => $region,
    'version' => 'latest',
    'credentials' => [
        'key' => $key,
        'secret' => $secret,
    ]
]);

$s3->registerStreamWrapper();


$context = stream_context_create(array(
    's3' => array(
        'seekable' => true
    )
));

// get the file's mime type to send the correct content type header
$path = "s3://$bucketname/$objectkey";

header('HTTP/1.0 200 OK');
header("Content-Type: video/mp4");
header('Accept-Ranges: bytes');

$options = array(
    "ssl" => array(
        "verify_peer" => false,
        "verify_peer_name" => false,
    ),
);

$context = stream_context_create($options);
$handle = fopen($path, 'rb', false, $context);

$chunkSize = 1024 * 1024 * 8;
$buffer = '';

ob_start();
while (!feof($handle)) {
    $buffer = fread($handle, $chunkSize);
    echo $buffer;
    ob_flush();
    flush();
}
fclose($handle);
exit;