index.php
<?php

$name = $address = $email = "";
$nameErr = $addressErr = $emailErr = "";

    If($_SERVER["REQUEST_METHOD"] == "POST"){

        if(empty ($_POST ["name"])){
            $nameErr = "name is required!";
        }else{
            $name = $_POST["name"];
        }

        if(empty ($_POST ["address"])){
            $addressErr = "address is required!";
        }else{
            $address = $_POST["address"];
        }

        if(empty ($_POST ["email"])){
            $emailErr = "email is required!";
        }else{
            $email = $_POST["email"];
        }

    }
?>

<style>
 .error{
     color: red;
 }
 </style>

<form method="post" action="<?php htmlspecialchars("PHP_SELF");?>">

    <input type="text" name="name" value=""><br>
    <span class="error"><?php echo $nameErr; ?></span><br>
    <input type="text" name="address" value=""><br>
    <span class="error"><?php echo $addressErr; ?></span><br>
    <input type="text" name="email" value=""><br>
    <span class="error"><?php echo $emailErr; ?></span><br>
    <input type="submit" value="submit">


</form>

<hr>

<?php
    include("connections.php");
    if($name && $address && $email) {

        $query = mysqli_query($connections, "INSERT INTO mytbl(name,address,email) VALUES('$name','$address','$email') ");

        echo "<script language='javascript'>alert('New Record Has been Inserted!')</script>";
        echo "<script> window.location.href='index.php';<script>";

    }

    $view_query = mysqli_query($connections, "SELECT * FROM mytbl");
    echo "<table border = '1' width = '50%'>";


    while($row = mysqli_fetch_assoc ($view_query)) {

        $db_name = $row["name"];
        $db_address = $row["address"];
        $db_email = $row["email"];

        echo "<tr>
        <td>$db_name</td>
        <td>$db_address</td>
        <td>$db_email</td>
    </tr>";

    }
        echo "</table>";


?>