In developing a PHP-based photo-CMS, what are some key features to consider, such as tagging, responsiveness, and user roles?

When developing a PHP-based photo-CMS, some key features to consider include tagging for organizing and categorizing photos, responsiveness for ensuring the CMS works well on various devices, and user roles for managing permissions and access levels.

// Example code for implementing tagging feature
// Add tags to photos
$photo_tags = array('nature', 'landscape', 'mountains');
// Store tags in database or metadata of the photo

// Example code for implementing responsiveness
// Use CSS media queries to adjust layout based on screen size
@media only screen and (max-width: 600px) {
    // CSS styles for smaller screens
}

// Example code for implementing user roles
// Define different user roles with specific permissions
$user_roles = array(
    'admin' => array('create', 'edit', 'delete'),
    'editor' => array('edit', 'delete'),
    'viewer' => array('view')
);
// Check user role before allowing access to certain features
if (in_array('edit', $user_roles['admin'])) {
    // Allow editing functionality
}