如果没有上传文件，如何编写php逻辑

我想做一个更新个人资料页面。当用户上传图片时，它将更新到数据库并更改

$\u会话['profilepic']

。但是，如果用户不想更新其配置文件图像，不想更改数据库值，而只想更改其他数据。如果“文件未上传，更新图像以外的其他值，不更改会话”，我如何编写逻辑，因为我无法将存储的img置于输入文件值，以确保数据库中的图像保持不变且未更新

这是我的php代码：

 if(isset($_POST['profile_update_btn']))
{
    $username = $_SESSION['username'];
    $profimage = $_FILES['profileimage']['name'];
    $fullname = $_POST['fullname'];
    $email =$_POST['email'];
    $phone = $_POST['phonenum'];

    $query = "UPDATE students SET fullName='$fullname',email = '$email', phoneNum='$phone', profilePic='$profiimage'  WHERE email = '$username'";
    $query_run = mysqli_query($connection,$query);

    if($query_run)
    {
        move_uploaded_file($_FILES["profileimage"]["tmp_name"],"prof/".$_FILES["profileimage"]["name"]);
        $_SESSION['profilepic'] = $profimage;
        $_SESSION['success']= "Profile Updated";
        header('Location: user_profile.php');
    }
    else
    {
        $_SESSION['status']= "Profile Not Updated";
        header('Location: user_profile.php');
    }

} 

---

上载文件时，

$\u文件

将以文件名字段的键填充数组中的值

  'profileimage' => 
    array (size=5)
      'name' => string '' (length=0)
      'type' => string '' (length=0)
      'tmp_name' => string '' (length=0)
      'error' => int 4
      'size' => int 0

实际值可能类似于：

  'profileimage' => 
    array (size=5)
      'name' => string 'v35.doc' (length=7)
      'type' => string 'application/octet-stream' (length=24)
      'tmp_name' => string 'F:\wamp64\tmp\php37EA.tmp' (length=25)
      'error' => int 0
      'size' => int 45568

因此，您可以这样做：

if (empty($_FILES['profileimage']['name'])) {
    //Do whatever you want when no upload...
}