update_accessed.php

<?php
session_start();
$metadataFile = 'data/files.json';

function loadMetadata() {
    global $metadataFile;
    if (!file_exists($metadataFile)) return ['files' => []];
    return json_decode(file_get_contents($metadataFile), true);
}

function saveMetadata($metadata) {
    global $metadataFile;
    file_put_contents($metadataFile, json_encode($metadata, JSON_PRETTY_PRINT));
}

if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['fileId'])) {
    $fileId = $_POST['fileId'];
    $metadata = loadMetadata();
    foreach ($metadata['files'] as &$file) {
        if ($file['id'] === $fileId) {
            $file['accessed'] = time();
            saveMetadata($metadata);
            echo json_encode(['success' => true]);
            exit;
        }
    }
    echo json_encode(['success' => false]);
}
?>