Notice: Undefined index [duplicate]

I do not know why you're giving this error, I've already reviewed everything.

Notice: Undefined index: firstName in C: \ xampp \ htdocs \ project \ log.php on line 14

Notice: Undefined index: last name in C: \ xampp \ htdocs \ project \ log.php on line 15

Notice: Undefined index: matricula in C: \ xampp \ htdocs \ project \ record.php on line 16

Notice: Undefined index: email in C: \ xampp \ htdocs \ project \ log.php on line 17

Notice: Undefined index: password in C: \ xampp \ htdocs \ project \ log.php on line 18

<?php 

    $username = 'root';
    $password = '';
    $connection = new PDO( 'mysql:host=localhost;dbname=*****', $username );

    $query = "INSERT INTO usuario (nome, sobrenome, matricula, email, senha) 
          VALUES (:nome, :sobrenome, :matricula, :email, :senha)";

    $statement = $connection->prepare($query);


    $valores = array();
    $valores[':nome'] = $_POST['primeiroNome'];
    $valores[':sobrenome'] = $_POST['sobrenome'];
    $valores[':matricula'] = $_POST['matricula'];
    $valores[':email'] = $_POST['email'];
    $valores[':senha'] = $_POST['senha'];





    $result = $statement->execute($valores);




    ?>

This is my form

<form  method="POST" action ="" name="for">
               <div class="form-group">
                  <div class="form-row">
                     <div class="col-md-6">
                        <label for="primeiroNome">Primeiro nome</label>
                        <input type="text" class="form-control" id="primeiroNome" name="primeiroNome" placeholder="Digite seu primeiro nome">
                     </div>
                     <div class="col-md-6">
                        <label for="Sobrenome">Sobrenome</label>
                        <input type="text" class="form-control" id="Sobrenome" name="sobrenome" placeholder="Digite seu Sobrenome">
                     </div>
                  </div>
               </div>
               <div class="col-md-6" id="matricula">
                  <label for="primeiroNome">Matrícula</label>
                  <input type="text" class="form-control"  name="matricula" placeholder="Digite sua matrícula">
               </div>
               <div class="form-group">
                  <label for="email">E-mail</label>
                  <input type="email" class="form-control" id="email" name="email" placeholder="Digite seu email">
               </div>
               <div class="form-group">
                  <div class="form-row">
                     <div class="col-md-6">
                        <label for="senha">Senha</label>
                        <input type="password" class="form-control" id="senha" name="senha" placeholder="Digite sua senha">
                     </div>
                     <div class="col-md-6">
                        <label for="confirmaSenha">confirmar senha</label>
                        <input type="password" class="form-control" id="confirmaSenha" name="confirmaSenha" placeholder="Confirme sua senha">
                     </div>
                  </div>
               </div>
               <div>
                  <input type="submit" class="btn btn-primary btn-block" href="registro.php" value="Registra-se"/>
               </div>
               <div class="text-center">
                  <a href="#" class="d-block small mt-3">Esqueceu sua senha?</a>
                  <a href="#" class="d-block small mt-3">Login?</a>
               </div>
            </form>