print_sessions.php

<?php

    $output = '';
    foreach (scandir(session_save_path()) as $x => $dir) {
        if (!preg_match('/^sess_(.*)/', $dir, $matches)) continue;

        ob_start();

        session_id($matches[1]);
        session_start();

        echo "SESSION({$matches[1]}): ";
        print_r($_SESSION);
        echo "\n";

        session_write_close();

        $output .= ob_get_clean();
    }

    echo($output);

?>