<section class="target">
    <div class="container">
        <div class="row">
            <div class="col-lg-8">
                <h2>Зарегистированно участников:</h2>
                <?php
                        include 'bd.php';

                        $results = mysql_query("SELECT COUNT(1) FROM register_user");
                        $arrays = mysql_fetch_array($results);

                        while ($arrays = mysql_fetch_array($results)) {
                            echo ""."<p>".$results."</p>"."";
                        }
                ?>
            </div>
        </div>
    </div>
</section>

<section class="target">
    <div class="container">
        <div class="row">
            <div class="col-lg-8">
                <h2>Зарегистированно участников:</h2>
    <?php
    $servername = "localhost";
    $username = "username";
    $password = "password";
    $dbname = "myDB";

    // Create connection
    $conn = new mysqli($servername, $username, $password, $dbname);
    // Check connection
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }

    $sql = "SELECT COUNT(1) as Count FROM register_user";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        // output data of each row
        while($row = $result->fetch_assoc()) {
            echo $row["Count"]";
        }
    } else {
        echo "0 results";
    }
    $conn->close();
    ?>
       </div>
        </div>
    </div>
</section>