add-contact.php脚本两次插入mysql

Question

我有一个add-contact.php的脚本，它使用MySQLi和PHP将我的表单数据添加到我的SQL数据库中，它运行成功，但是，当我点击提交时，它会发布表单数据TWICE！

以下是add-contact.php的代码

if($link === false){
    die("ERROR: Could not connect. " . mysqli_connect_error());
}

$category = mysqli_real_escape_string($link, $_POST['category']);
$name = mysqli_real_escape_string($link, $_POST['name']);
$url = mysqli_real_escape_string($link, $_POST['url']);
$email = mysqli_real_escape_string($link, $_POST['email']);
$notes = mysqli_real_escape_string($link, $_POST['notes']);


$sql = "INSERT INTO contacts (category, name, url, email, notes) VALUES ('$category', '$name', '$url', '$email', '$notes')";
if(mysqli_query($link, $sql)){
    echo "
      <div class='wrapper'>
        <h1>Panda successfully added!</h1>
        <h2>You are being redirected in 5 seconds.</h2>
      </div>
    ";
} else{
    echo "ERROR: Could not able to execute $sql. " . mysqli_error($link);
}

mysqli_close($link);

只是想知道是否有人知道是什么导致它两次插入数据库？...