Version checking guidance is wrong

Perhaps we should include a corrected version of this_plugin_version_check_for_updates from Zen Colorbox in the core:
    // Respect the admin setting for version checking to prevent checking this if the store is disabled. (typically set because the version checker may generate warnings/errors.
    if (constant($module_constant . '_PLUGIN_CHECK') && !function_exists('this_plugin_version_check_for_updates')) {
        function this_plugin_version_check_for_updates($plugin_file_id = 0, $version_string_to_compare = '', $strict_zc_version_compare = false)
        {
            if ($plugin_file_id == 0) return false;
            $new_version_available = false;
            $lookup_index = 0;
            $url1 = 'https://plugins.zen-cart.com/versioncheck/'.(int)$plugin_file_id;
            $url2 = 'https://www.zen-cart.com/versioncheck/'.(int)$plugin_file_id;

            $ch = curl_init();
            curl_setopt($ch, CURLOPT_URL,$url1);
            curl_setopt($ch, CURLOPT_VERBOSE, 0);
            curl_setopt($ch, CURLOPT_HEADER, false);
            curl_setopt($ch, CURLOPT_TIMEOUT, 9);
            curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 9);
            curl_setopt($ch, CURLOPT_USERAGENT, 'Plugin Version Check [' . (int)$plugin_file_id . '] ' . HTTP_SERVER);
            curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
            $response = curl_exec($ch);
            $error = curl_error($ch);
            $errno = curl_errno($ch);

            if ($error > 0) {
                trigger_error('CURL error checking plugin versions: ' . $errno . ':' . $error . "\nTrying http instead.");
                curl_setopt($ch, CURLOPT_URL, str_replace('tps:', 'tp:', $url1));
                $response = curl_exec($ch);
                $error = curl_error($ch);
                $errno = curl_errno($ch);
            }
            if ($error > 0) {
                trigger_error('CURL error checking plugin versions: ' . $errno . ':' . $error . "\nTrying www instead.");
                curl_setopt($ch, CURLOPT_URL, str_replace('tps:', 'tp:', $url2));
                $response = curl_exec($ch);
                $error = curl_error($ch);
                $errno = curl_errno($ch);
            }
            curl_close($ch);
            if ($error > 0 || $response == '') {
                trigger_error('CURL error checking plugin versions: ' . $errno . ':' . $error . "\nTrying file_get_contents() instead.");
                $ctx = stream_context_create(array('http' => array('timeout' => 5)));
                $response = file_get_contents($url1, null, $ctx);
                if ($response === false) {
                    trigger_error('file_get_contents() error checking plugin versions.' . "\nTrying http instead.");
                    $response = file_get_contents(str_replace('tps:', 'tp:', $url1), null, $ctx);
                }
                if ($response === false) {
                    trigger_error('file_get_contents() error checking plugin versions.' . "\nAborting.");
                    return false;
                }
            }

            $data = json_decode($response, true);
            if (!$data || !is_array($data)) return false;
            // compare versions
            if (strcmp($data[$lookup_index]['latest_plugin_version'], $version_string_to_compare) > 0) $new_version_available = true;
            // check whether present ZC version is compatible with the latest available plugin version
            $zc_version = PROJECT_VERSION_MAJOR . '.' . preg_replace('/[^0-9.]/', '', PROJECT_VERSION_MINOR);
            if ($strict_zc_version_compare) $zc_version = PROJECT_VERSION_MAJOR . '.' . PROJECT_VERSION_MINOR;
            if (!in_array('v'. $zc_version, $data[$lookup_index]['zcversions'])) $new_version_available = false;
            return ($new_version_available) ? $data[$lookup_index] : false;
        }
    }

    // Version Checking
    // Respect the admin setting for version checking to prevent checking this if the store is disabled. (typically set because the version checker may generate warnings/errors.
    if ($zencart_com_plugin_id != 0 && isset($_GET['gID']) && $_GET['gID'] == $configuration_group_id && (!defined($module_constant . '_PLUGIN_CHECK') || constant($module_constant . '_PLUGIN_CHECK'))) {
        $new_version_details = this_plugin_version_check_for_updates($zencart_com_plugin_id, $current_version);
        if ($new_version_details != false) {
            $messageStack->add("Version ".$new_version_details['latest_plugin_version']." of " . $new_version_details['title'] . ' is available at <a href="' . $new_version_details['link'] . '" target="_blank">[Details]</a>', 'caution');
        }
    }
zencart / documentation

Version checking guidance is wrong #961
