How to Implement Pagination with API Using PHP [closed]

I’m working with the Clinical Trials API to retrieve study data using PHP. Currently, I can pull through the first 10 results as thats the default, but I’m struggling to implement pagination to access the remaining records.

I’ve tried using PHP sessions to handle the nextPageToken for pagination, but I’m having trouble utilizing the token properly. Ideally, I want to load more results incrementally (e.g 10 at a time) without fetching all the data at once, because it obviously causes my site to time out.

Here’s my code I’m currently working with

defined('ABSPATH') || exit;

// Enqueue custom CSS
function register_custom_styles() {
    wp_enqueue_style('custom-shortcode-style', get_template_directory_uri() . '/style.css', [], '1.0.0');
}
add_action('wp_enqueue_scripts', 'register_custom_styles');

// Register shortcode
add_shortcode('external_data', 'fetch_clinical_trials');

function fetch_clinical_trials($atts) {
    if (is_admin()) {
        return '<p>Shortcode [external_data] preview.</p>';
    }

    $atts = shortcode_atts(['title' => 'Clinical Trials Data'], $atts, 'external_data');

    $response = wp_remote_get('https://clinicaltrials.gov/api/v2/studies');
    if (is_wp_error($response)) {
        return 'Error fetching data.';
    }

    $studies = json_decode(wp_remote_retrieve_body($response), true)['studies'] ?? [];

    $html = '<h2>' . esc_html($atts['title']) . '</h2>';
    $html .= '<table>
                <tr><th>NCT ID</th><th>Organization</th><th>Title</th><th>Status</th><th>Start Date</th><th>Completion Date</th><th>Sponsor</th></tr>';

    foreach ($studies as $study) {
        $html .= '<tr>';
        $html .= '<td>' . esc_html($study['protocolSection']['identificationModule']['nctId'] ?? 'N/A') . '</td>';
        $html .= '<td>' . esc_html($study['protocolSection']['identificationModule']['organization']['fullName'] ?? 'N/A') . '</td>';
        $html .= '<td>' . esc_html($study['protocolSection']['identificationModule']['briefTitle'] ?? 'N/A') . '</td>';
        $html .= '<td>' . esc_html($study['protocolSection']['statusModule']['overallStatus'] ?? 'N/A') . '</td>';
        $html .= '<td>' . esc_html($study['protocolSection']['statusModule']['startDateStruct']['date'] ?? 'N/A') . '</td>';
        $html .= '<td>' . esc_html($study['protocolSection']['statusModule']['primaryCompletionDateStruct']['date'] ?? 'N/A') . '</td>';
        $html .= '<td>' . esc_html($study['protocolSection']['sponsorCollaboratorsModule']['leadSponsor']['name'] ?? 'N/A') . '</td>';
        $html .= '</tr>';
    }

    $html .= '</table>';
    return $html;
}

I understand there’s a nextPageToken for pagination, but I can’t figure out how to correctly use it to fetch subsequent results. How can I implement a proper pagination mechanism for this scenario?

Any advice or examples on how to properly handle this token for paginated requests would be greatly appreciated! Thank you !