如何使用PHP表单一次上传多个图像？

Here, my php script for upload image in server. i want user can upload multiple images on one records. right now, in this code at time only one image can post, user's requirement is they can post multiple images at time. I don't idea how can I possible using arrays. please help. Thanks in advance :)

<?php
  include ("connect.php");
  if(isset($_POST['submit']))
 {
$event = $_POST['evnt_name'];
$image_name = $_FILES['evnt_img']['name'];
$image_type = $_FILES['evnt_img']['type'];
$image_size = $_FILES['evnt_img']['size'];
$image_tmp = $_FILES['evnt_img']['tmp_name'];

if($event=='' && $image_name==''){

    echo "<script>alert('Any field is empty')</script>";
    exit();
}
if($image_type=="image/jpeg" OR $image_type=="image/png" OR     $image_type=="image/gif")
{
    if($image_size<=50000)
    {
      move_uploaded_file($image_tmp,"imagess/$image_name");
    }
    else
    {
        echo "<script>alert('image is large, only 50kb size allowed')</script>";
        exit();
    }

}
else{
    echo "<script>alert('image type is invalid')</script>";
    exit();
}

$query = "insert into event_update (evnt_text,evnt_img) values  ('$event','$image_name')";

   if(mysqli_query($conn,$query))
   {
    echo "<script>alert('Post has been published')</script>";
    exit();
   }
 }
?>

And below my simple bootstrap HTML code for form

<div class="col-lg-12">
    <form method="POST" action="evntform.php" enctype="multipart/form-data">
        <div class="form-group">
            <label>Events Name</label>
            <input type="text" name="evnt_name" placeholder="Write Events Name" class="form-control">
        </div>
        <div class="form-group">
            <label>File input</label>
            <input type="file" name="evnt_img[]">
        </div>
        <button name="submit" type="submit" class="btn btn-default">Submit Button</button>
    </form>
</div>