php display error message when input value is empty: so with if(!isset.....) on the same page

Question

I'm adding a html form to my website. I have an issue with the form validation. I'm trying to display error message when the user does not writte is email address and still submit the form. The thing is: I'm trying to do it on the same page: so my code, as it is now, directly display the error message when the page is loaded (which is normal because the user did not enter is email address yet).

I would like this message to display on the same page (so here: on registerForm.php) only if the user clicked on the submit btn but did not enter his email address. Could someone help me please?

I put the code bellow:

registerForm.php

`

<?php
session_start();

 //include a javascript file
 echo "<script type='text/javascript' src='registerForm.js'></script>";
?>

<div class="divCenter">
<div class="registerform-container">
    <form action="successForm.php" class="registerform-form" method="POST">
        <div>
            <label id="emailInput" for="email" class="registerform-form-label">Email</label>
            <div>
            <input type="email" class="registerform-form-control" id="email" name="email" aria-describedby="email-subscribe" placeholder="you@exemple.com">
            <div id="email-help" class="registerform-form-text">L'email utilisé lors de la création de compte.</div>
            </div>
        </div>
            <button id="button" class="registerform-btn disabled"  type="submit">Send</button>
   </form>
    <?php
        if(isset($_SESSION['statut'])){
    ?>
        <div class="success">
            <p><?php echo htmlspecialchars($_SESSION['statut']) ?></p>
        </div>';    
    <?php
       
        //une fois afficher il faut détruire le session
        unset($_SESSION['statut']);
        }

    ?>
</div>
</div>

successForm.php

<?php
   //include CSS Style Sheet
   echo "<link rel='stylesheet' type='text/css' href='registerForm.css' />";
   //include a javascript file
   echo "<script type='text/javascript' src='rfffff.js'></script>";
?>

<?php
if(!isset($_SESSION)) 
{ 
    session_start(); 
} 
?>

<?php
if(!isset($_POST['email']))
{
  echo 'you must enter your email address'; return;
    }

    try
    {
    $db = new PDO('mysql:host=localhost;dbname=mariawebsite;charset=utf8', 'root', 'root');
    }
    catch (Exception $e)
    {
        die('Erreur : ' . $e->getMessage());
    }

    $email = $_POST['email'];
    // Préparation
    $insertEmail = $db->prepare("INSERT INTO users_addresses(email) VALUES (:email)");
    // ajouter la ligne ci-dessous pour être sûr d'afficher toutes les erreurs.
    $db->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
    // Exécution ! La recette est maintenant en base de données
    $insertEmail->execute([
    'email' => $email,
    ]);
    $_SESSION['statut'] = "$email submited successfully";
    header('Location: home.php');
?>

`

I would like this message to display on the same page (so here: on registerForm.php) only if the user clicked on the submit btn but did not enter his email address. Could someone help me please?

Answer 1

Try this: On successForm.php

if(!isset($_POST['email']) || empty($_POST['email']))
{
  $msg =  'you must enter your email address';
 header('Location: registerForm.php?msg='.$msg); // this will redirect to register form with message

} else {
 //try catch and other code here
}

On registerForm.php After and before form starts. Add this:

<?php if(isset($_GET['msg']) && $_GET['msg'] != "") {?>
        <div class="msg_error">
            <p><?php echo $_GET['msg']?></p>
        </div>
<?php } ?>