刷新页面时，表单数据重新发布到数据库

Question

I'm trying to learn how to make a registration form that publishes data to a database. I couldn't get the code from a tutorial to work until I stripped it down. It now works OK, except that if I refresh the page (to remove the values I typed in so I can type in another entry), it republishes the original data to the database table.

In other words, if I type in the values Kelly Kau for firstname and lastname, then hit the Submit button, Kelly and Kau are entered in the database table. But when I refresh the page, another row with Kelly and Kau is added.

Is there a way to stop this? I'm working with PHP and MySQL. The tutorial I'm trying to copy is jQuery. Eventually, I may add some AJAX, too.

<form id="signupform" autocomplete="off" method="post" action="" novalidate>
  <table>
    <tr>
    <td class="label"><label id="lfirstname" for="firstname">First Name</label></td>
    <td class="field"><input id="firstname" name="firstname" type="text" value="" maxlength="100"></td>
    <td class="status"></td>
  </tr>
  <tr>
    <td class="label"><label id="llastname" for="lastname">Last Name</label></td>
    <td class="field"><input id="lastname" name="lastname" type="text" value="" maxlength="100"></td>
    <td class="status"></td>
  </tr>
  <tr>
    <td class="label"><label id="lsignupsubmit" for="signupsubmit">Signup</label></td>
    <td class="field" colspan="2"><input id="signupsubmit" name="signup" type="submit" value="Signup"></td>
  </tr>
</table>
</form>
<?php
include('ajax-database/config.php');
$pdo = connect();

try {
  $sql = "INSERT INTO g1_members (firstname, lastname) VALUES  (:firstname, :lastname)";
 $query = $pdo->prepare($sql);
 $query->bindParam(':firstname', $_POST['firstname'], PDO::PARAM_STR);
 $query->bindParam(':lastname', $_POST['lastname'], PDO::PARAM_STR);

 $query->execute();
} catch (PDOException $e) {
 echo 'PDOException : '.  $e->getMessage();
}
?>

Answer 1

Use a conditional statement based on your submit button being clicked:

<?php
include('ajax-database/config.php');
$pdo = connect();

if(isset($_POST['signup'])){

try {
  $sql = "INSERT INTO g1_members (firstname, lastname) VALUES  (:firstname, :lastname)";
 $query = $pdo->prepare($sql);
 $query->bindParam(':firstname', $_POST['firstname'], PDO::PARAM_STR);
 $query->bindParam(':lastname', $_POST['lastname'], PDO::PARAM_STR);

 $query->execute();

} catch (PDOException $e) {
 echo 'PDOException : '.  $e->getMessage();
}

} // brace for if(isset($_POST['signup']))

?>

or a header redirection on successful query:

if($query){
header("Location: http://www.example.com");
exit;
}

---

• Ideally, if you don't want the same values to be inserted, then it would be best to set the given column(s) as UNIQUE.