Problem Analysis

To get information about installed plugins, which provides plugin’s version, we’ll use get_plugins() function. Keep in mind, that this function is available in back end only, so our code must reside there. Data, returned from this function, does not tell us, which plugins are active. To filter out active plugins, we’ll use get_option('active_plugins') function. It will return a simple array, consisting of keys to array returned by get_plugins() function.

Code

The best illustration for our method will be the actual code. We’ll create a dashboard widget, displaying three-column table, showing active plugin’s name, its current version, and its newest version in WordPress repository. Let’s create myDashboardWidget.php file, and put the code below, in it.

<?php
if(is_admin()) { // make sure, the following code runs in back end

    // returns version of the plugin represented by $slug, from repository
    function getPluginVersionFromRepository($slug) {
        $url = "https://api.wordpress.org/plugins/info/1.2/?action=plugin_information&request[slugs][]={$slug}";
        $response = wp_remote_get($url); // WPOrg API call   
        $plugins = json_decode($response['body']);

        // traverse $response object
        foreach($plugins as $key => $plugin) {
            $version = $plugin->version;
        }
        return $version;
    }

    // dashboard widget's callback
    function activePluginsVersions() {
        $allPlugins = get_plugins(); // associative array of all installed plugins
        $activePlugins = get_option('active_plugins'); // simple array of active plugins

        // building active plugins table
        echo '<table width="100%">';
        echo '<thead>';
        echo '<tr>';
        echo '<th width="50%" style="text-align:left">Plugin</th>';
        echo '<th width="20%" style="text-align:left">currVer</th>';
        echo '<th width="20%" style="text-align:left">repoVer</th>';
        echo '</tr>';
        echo '</thead>';
        echo '<tbody>';

        // traversing $allPlugins array
        foreach($allPlugins as $key => $value) {
            if(in_array($key, $activePlugins)) { // display active only
                echo '<tr>';
                echo "<td>{$value['Name']}</td>";
                echo "<td>{$value['Version']}</td>";
                $slug = explode("https://wordpress.stackexchange.com/",$key)[0]; // get active plugin's slug

                // get newest version of active plugin from repository
                $repoVersion = getPluginVersionFromRepository($slug);

                echo "<td>{$repoVersion}</td>";
                echo '</tr>';
            }
        }
        echo '</tbody>';
        echo '</table>';
    }     

    // widget's registration
    function fpwAddDashboardWidget() {
        wp_add_dashboard_widget(
            'active_plugins_versions', // widget's ID
            'Active Plugins Versions', // widget's title
            'activePluginsVersions'    // widget's callback (content)
        );  
    }
    add_action('wp_dashboard_setup', 'fpwAddDashboardWidget');
}

Now, place this file in /wp-content/mu-plugins/ directory.

Code Explained

Read comments within myDashboardWidget.php file.

Note: if there is no version shown in third column of the table, the plugin is not in repository (either premium, or discontinued).

Code Efficiency

Efficiency of this sample code can be much improved. The WPOrg API request is made for each plugin. /plugins/info/1.2/ version of the API, allows getting info for all plugin slugs with one request only.