Bonjour, j'ai un projet en PHP sur organiser des formations.
Intro : les admin créent des programmes(matières) et à partir de ces programmes, ils organisent des formations(cours)

Et ici, une personne s'occupe d'entrer tous les personnes qui veulent participer aux formations. 

Le problème ici c'est que je n'arrive pas à renvoyer les données du formulaire où on peut inscrire les données des participants par rapport à la formation qu'il a choisi.

Ce code est la page où on voit la formation créée et que l'on souhaite participer :

<a href="participer.php?participer=<?php echo $row['formaID']?>" class="btn" 
                    style="color:white;background:#FFBC42"
                    onmouseover="this.style.background='#f1ac2c';this.style.color='white';"
                    onmouseout="this.style.background='#FFBC42';this.style.color='white';">Participer</a>

Ce code est le formulaire pour ajouter les participants en fonction de la formation choisi participer.php :

<?php 
include '../model/creerForm.php';
include '../model/creerServices.php';
include '../model/participant.php';
$creerForm = new creerForm;
$creerServices = new creerServices;
$participant = new participant;
$rowsall = $creerForm->getAllForm();
$rowsallService = $creerServices->getAllService();

$id = $_REQUEST['participer'];
$row = $creerForm->viewForm($id);
$insert = $participant->participant();
?>
<div class="container-fluid">
        <br><br>
    <div>
        <?php if(!empty($row)) { 
            var_dump($row);?>

        
        <a href="index_demandeur.php"><button class="btn btn-secondary">Retour</button> </a>
        <h1 style="color:#FFBC42;text-align:center;margin-top:-50px" ><b>Participer à la formation</b></h1>
    <?php
    } ?>
    </div>

    <div class="container w-75" style="margin-top: 50px;">
        <div class="card" id="participer">
            <div class="row">
                <div class="col-md-7"><img src="../admin/<?php echo $row[0]['imageProgramme'];?>" class="img-fluid rounded-start" alt="..."></div>

                <div class="col-md-5">   
                    <div class="card-body">  
                        <h3 class="card-title"  style="color:#FFBC42"><?php echo $row[0]['programme']?> </h3>
                        <form action="" method="post" enctype="multipart/form-data" style="margin-top: 30px;">
                            <div class="row">
                                <div class="col">
                                    <div class="form-floating mb-3">
                                        <input name="nomParticipant" id="nomParticipant" 
                                        class="form-control" required aria-label="With textarea" type="text" placeholder="Description du programme">
                                        <label for="floatingInput">Nom</label>
                                    </div>
                                </div>
                                <div class="col">
                                    <div class="form-floating mb-3">
                                        <input name="prenomParticipant" id="prenomParticipant" 
                                        class="form-control" required aria-label="With textarea" type="text" placeholder="Description du programme">
                                        <label for="floatingInput">Prénom</label>
                                    </div>
                                </div>
                            </div>
                            
                            <div class="form-floating mb-3">
                                <input name="fonctionParticipant" id="fonctionParticipant" 
                                class="form-control" required aria-label="With textarea" type="text" placeholder="Description du programme">
                                <label for="floatingInput">Fonction/poste occupé</label>
                            </div>

                            <select class="form-select" name="serviceParticipant" aria-label="Default select example" 
                            id="serviceParticipant" required>
                                <option disabled selected>Service</option>

                                <!-- Service ajouté depuis creerService -->   
                                <optgroup label="Les services ajoutés">
                                    <?php
                                        if(!empty($rowsallService)) {
                                        foreach($rowsallService as $rowService) {
                                    ?>  
                                        <option value="<?php echo $rowService['nomService']?>"><?php echo $rowService['nomService']?></option>
                                    <?php }
                                        }
                                    ?>
                                </optgroup>
                            </select> <br>
                            <a href="../demandeur/index_demandeur.php"><button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Annuler</button></a>
                            <button type="submit" class="btn btn-warning" style="color:white">Inscrire le participant</button>
                            </div>
                        
                        
                        
                        </form>                
                    </div>                    
                </div>

            </div>
            <br><br><br>
            

        </div>

    </div>

mon fichier pour créer les participants participants.php :

    <?php 
        class participant {

            private $server = "localhost";
            private $username = "root";
            private $password = "";
            private $db = "formation_db";
            private $conn;

            public function __construct()
            { 
                try {
                    $this->conn = new mysqli(
                                    $this->server, 
                                    $this->username, 
                                    $this->password,
                                    $this->db 
                                );
            }   catch(Exception $e) 
            {
                echo "Erreur de connexion" . $e->getMessage();
            }
        }

        function participant(){
            if(isset($_POST['nomParticipant']) && isset($_POST['prenomParticipant']) && isset($_POST['fonctionParticipant']) && isset($_POST['serviceParticipant'])) {
                $nomParticipant = $_POST['nomParticipant'];
                $prenomParticipant = $_POST['prenomParticipant'];
                $fonctionParticipant = $_POST['fonctionParticipant'];
                $serviceParticipant = $_POST['serviceParticipant'];

                if(empty($nomParticipant)) {
                    header('Location: index_demandeur.php?error=Nom du participant requis');
                    exit();
                } else {
                    $query = "INSERT INTO participant (nomParticipant, prenomParticipant, fonctionParticipant, serviceParticipant) 
                    VALUES ('$nomParticipant', '$prenomParticipant', '$fonctionParticipant', '$serviceParticipant')";
                    if($sql = $this->conn->query($query)) {

                        echo "     
                        <head>
                            <meta charset='utf-8'>
                            <meta name='viewport' content='width=device-width,initial-scale=1.0'>
                            <title>Form&nou - Participer</title>
                            <!-- CSS only -->
                            <link href='https://cdn.jsdelivr.net/npm/bootstrap@5.1.0/dist/css/bootstrap.min.css' rel='stylesheet' integrity='sha384-KyZXEAg3QhqLMpG8r+8fhAXLRk2vvoC2f3B09zVXn8CA5QIVfZOJ3BCsw2P0p/We' crossorigin='anonymous'>
                            <link rel='stylesheet' href='https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css' integrity='sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T' crossorigin='anonymous'>
                            <link href='https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css'>
                            <script src='https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.bundle.min.js'></script>
                            <script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js'></script>
                            <script src='https://kit.fontawesome.com/6c1ecc43dd.js' crossorigin='anonymous'></script>
                            <link rel='stylesheet' href='../Public/css/style.css'>
                            <link rel='stylesheet' href='../Public/css/style_admin.css'>
                            <link rel='stylesheet' href='../Public/css/header.css'>
                            <link rel='preconnect' href='https://fonts.googleapis.com'>
                            <link rel='preconnect' href='https://fonts.gstatic.com' crossorigin>
                            <link href='https://fonts.googleapis.com/css2?family=Roboto:ital,wght@0,100;0,300;0,400;0,500;0,700;0,900;1,100;1,300;1,400;1,500;1,700;1,900&display=swap' rel='stylesheet'>
                    
                            <link href='https://fonts.googleapis.com/css?family=Roboto:300,400&display=swap' rel='stylesheet'>
                            <link href='https://fonts.googleapis.com/css?family=Poppins:300,400,500&display=swap' rel='stylesheet'>
                            <script src='https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js'></script>
                            <script src='https://cdn.jsdelivr.net/momentjs/2.14.1/moment.min.js'></script>
                            <script src='https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datetimepicker/4.17.37/js/bootstrap-datetimepicker.min.js'>
                            <link rel='stylesheet' href='../fonts/icomoon/style.css'>
                            <link rel='stylesheet' href='../Public/css/rome.css'>
                            <link rel='shortcut icon' type='image/png' href='../Public/img/bg.png'/>
                            <script src='https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datetimepicker/4.17.37/js/bootstrap-datetimepicker.min.js'></script>
                            <link rel='stylesheet' href='https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datetimepicker/4.17.37/css/bootstrap-datetimepicker.min.css'>
                    
                        </head>
                
                        <!-- Header -->
                            <div class='header__otherpage'>
                                <div class='header__texture'></div>
                                <div class='container__1'>
                                    <div class='header__navbar'>
                                        <div class='header__navbar--logo'>
                                            <a style='text-decoration:none' href='../demandeur/apropos_demandeur.php' class='header__navbar--logo-title'>Form&Nou</a>
                                        </div>
                                        <div class='header__navbar--menu'>
                                            <a style='text-decoration:none;color:white' href='../demandeur/index_demandeur.php' class='header__navbar--menu-link'><i class='fas fa-home'></i> Accueil</a>
                                            <a style='text-decoration:none;color:white' href='#' class='header__navbar--menu-link'>Les Participants</a>
                                            <a style='text-decoration:none;color:white' href='../demandeur/seFormer.php' class='header__navbar--menu-link'>Se Former</a>
                                            <a style='text-decoration:none;color:white' href='../demandeur/contact.php' class='header__navbar--menu-link'>Contact</a>
                                            <a style='text-decoration:none;color:white' href='../logout.php' class='header__navbar--menu-link'>Déconnexion</a>
                                            
                                        </div>
                    
                                        <div class='header__navbar-toggle'>
                                            <span class='header__navbar-toggle-icons'></span> 
                                        </div>
                                    </div>
                    
                                </div>
                    
                            </div>
                        <br><br><div class='card w-25' style='padding:20px;color: #FFBC42; margin:auto;'>
                        <h5 style='text-align:center'>
                        <i class='fas fa-check-circle'></i>  <b><q> ".$_POST['nomParticipant']." ".$_POST['prenomParticipant']." </q> 
                        a bien été enregistré pour cette formation</b></h5>
                        <a href='../demandeur/index_demandeur.php' style='color:grey;text-align:center'>Retour vers la page d'accueil</a>
                        </div>";
                        exit();
                    } else {
                        echo "
                        <head>
                            <meta charset='utf-8'>
                            <meta name='viewport' content='width=device-width,initial-scale=1.0'>
                            <title>Form&nou - Participer</title>
                            <!-- CSS only -->
                            <link href='https://cdn.jsdelivr.net/npm/bootstrap@5.1.0/dist/css/bootstrap.min.css' rel='stylesheet' integrity='sha384-KyZXEAg3QhqLMpG8r+8fhAXLRk2vvoC2f3B09zVXn8CA5QIVfZOJ3BCsw2P0p/We' crossorigin='anonymous'>
                            <link rel='stylesheet' href='https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css' integrity='sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T' crossorigin='anonymous'>
                            <link href='https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css'>
                            <script src='https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.bundle.min.js'></script>
                            <script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js'></script>
                            <script src='https://kit.fontawesome.com/6c1ecc43dd.js' crossorigin='anonymous'></script>
                            <link rel='stylesheet' href='../Public/css/style.css'>
                            <link rel='stylesheet' href='../Public/css/style_admin.css'>
                            <link rel='stylesheet' href='../Public/css/header.css'>
                            <link rel='preconnect' href='https://fonts.googleapis.com'>
                            <link rel='preconnect' href='https://fonts.gstatic.com' crossorigin>
                            <link href='https://fonts.googleapis.com/css2?family=Roboto:ital,wght@0,100;0,300;0,400;0,500;0,700;0,900;1,100;1,300;1,400;1,500;1,700;1,900&display=swap' rel='stylesheet'>
                    
                            <link href='https://fonts.googleapis.com/css?family=Roboto:300,400&display=swap' rel='stylesheet'>
                            <link href='https://fonts.googleapis.com/css?family=Poppins:300,400,500&display=swap' rel='stylesheet'>
                            <script src='https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js'></script>
                            <script src='https://cdn.jsdelivr.net/momentjs/2.14.1/moment.min.js'></script>
                            <script src='https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datetimepicker/4.17.37/js/bootstrap-datetimepicker.min.js'>
                            <link rel='stylesheet' href='../fonts/icomoon/style.css'>
                            <link rel='stylesheet' href='../Public/css/rome.css'>
                            <link rel='shortcut icon' type='image/png' href='../Public/img/bg.png'/>
                            <script src='https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datetimepicker/4.17.37/js/bootstrap-datetimepicker.min.js'></script>
                            <link rel='stylesheet' href='https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datetimepicker/4.17.37/css/bootstrap-datetimepicker.min.css'>
                    
                        </head>
                
                        <!-- Header -->
                            <div class='header__otherpage'>
                                <div class='header__texture'></div>
                                <div class='container__1'>
                                    <div class='header__navbar'>
                                        <div class='header__navbar--logo'>
                                            <a style='text-decoration:none' href='../demandeur/apropos_demandeur.php' class='header__navbar--logo-title'>Form&Nou</a>
                                        </div>
                                        <div class='header__navbar--menu'>
                                            <a style='text-decoration:none;color:white' href='../demandeur/index_demandeur.php' class='header__navbar--menu-link'><i class='fas fa-home'></i> Accueil</a>
                                            <a style='text-decoration:none;color:white' href='#' class='header__navbar--menu-link'>Les Participants</a>
                                            <a style='text-decoration:none;color:white' href='../demandeur/seFormer.php' class='header__navbar--menu-link'>Se Former</a>
                                            <a style='text-decoration:none;color:white' href='../demandeur/contact.php' class='header__navbar--menu-link'>Contact</a>
                                            <a style='text-decoration:none;color:white' href='../logout.php' class='header__navbar--menu-link'>Déconnexion</a>
                                            
                                        </div>
                    
                                        <div class='header__navbar-toggle'>
                                            <span class='header__navbar-toggle-icons'></span> 
                                        </div>
                                    </div>
                    
                                </div>
                    
                            </div>
                        
                        <br><br>
                        <aside class='w-25' style='background-color:white;box-shadow: 0px 4px 8px 0px rgba(0, 0, 0, 0.2);position:relative;
                        border-radius:5px;color:white;padding:10px;margin:auto'>
                            <h5 class='text-danger' style='text-align:center;margin-top:20px'><i class='fas fa-exclamation-triangle'></i> 
                                <b>Un problème est survenu!</b> <br>
                                <a href='../demandeur/index_demandeur.php' style='color:grey;text-align:center;font-size:16px'>Cliquez ici pour vous rediriger</a>
                            </h5>          
                        </aside><br><br><br>";
                        var_dump($_POST);
                        exit();
                    }
                }
            }
        }

        public function viewParticipant($id) {
            $data = null;
            $query = "SELECT participantID, formaChoisi, nomParticipant, prenomParticipant, fonctionParticipant, serviceParticipant FROM participant WHERE participantID = " . $id;
            if($sql = $this->conn->query($query)) {
                while($row = mysqli_fetch_assoc($sql)) {
                    $data[] = $row;
                }
            }
            return $data;   
        }  

        public function getAllParticipantByFormation($id_formation) {
            $data = null;
            $query = "SELECT P.participantID
            ,P.formaChoisi
            ,P.nomParticipant
            ,P.prenomParticipant
            ,P.fonctionParticipant
            ,P.serviceParticipant
            ,F.formaID 
            FROM participant P
            LEFT JOIN forma F ON P.formaChoisi = F.formaID
            ORDER BY formaID ASC
            WHERE formaID = '$id_formation'
            ORDER BY nomParticipant ASC";
            if($sql = $this->conn->query($query)) {
                while($row = mysqli_fetch_assoc($sql)) {
                    $data[] = $row;
                }
            }
            return $data;
        }   

    }
    ?>