modx_insta.php

<?php
$auth_redirect = $modx->makeUrl($modx->resource->id, '', '', 'full');

// token
if (isset($_GET['code'])) {
    $code = $_GET['code'];
    $ctx = stream_context_create(array(
        'http' => array(
            'method'  => 'POST',
            'header'  => 'Content-type: application/x-www-form-urlencoded',
            'content' => http_build_query(array(
                'client_id' => $client_id,
                'client_secret' => $client_secret,
                'grant_type' => 'authorization_code',
                'redirect_uri' => $auth_redirect,
                'code' => $code
            ))
        )
    ));
    $response = file_get_contents('https://api.instagram.com/oauth/access_token', false, $ctx);
    $json = json_decode($response, true);
    if (isset($json['access_token'])) {
        $token = $json['access_token'];
        $modx->runProcessor('system/settings/update', array(
            'key' => 'insta_token',
            'value' => $token,
            'namespace' => 'core'
        ));
        $modx->setOption('insta_token', $token);
        echo 'access granted';
    } else {
        $modx->log(xPDO::LOG_LEVEL_ERROR,'[Insta] Error retrieving token.');
    }
    return;
}

// auth
if (!isset($_GET['fetch'])) {
    $authUrl = 'https://api.instagram.com/oauth/authorize/?' . http_build_query(array(
        'client_id' => $client_id,
        'redirect_uri' => $auth_redirect,
        'scope' => 'basic public_content',
        // 'scope' => 'public_content',
        'response_type' => 'code'
    ));
    $modx->sendRedirect($authUrl);
    return;
}

if (isset($_GET['fetch'])) {
    $token = $modx->getOption('insta_token');
    if ($token) {
        $tagUrl = 'https://api.instagram.com/v1/tags/' . $tag_name . '/media/recent?count=12&access_token=' . $token;
        try {
            $response = file_get_contents($tagUrl);
            $json = json_decode($response, true);
            if (isset($json['data']) && is_array($json['data'])) {
                $images = array();
                foreach ($json['data'] as $image) {
                    if ($image['type'] != 'image') 
                        continue;
                    $images[] = array(
                        'src' => $image['images']['low_resolution']['url'],
                        'href' => $image['link']
                    );
                }
                echo json_encode($images);
            }
        } catch (Exception $ex) {
            $modx->log(xPDO::LOG_LEVEL_ERROR,'[Insta] Error fetching media: ' . $ex->getMessage());
        }
    } else {
        $modx->log(xPDO::LOG_LEVEL_ERROR,'[Insta] Authentication required.');
    }
}