displays a progress bar when uploading and displaying html page

Question

I tried to create a file upload , but when the upload progress bar appears when finished directly open the file that I uploaded , I uploaded file extension * .html

html

<div class="container">
  <div class="row">
     <form action="accept-file.php" method="post" enctype="multipart/form-data">
     Your Photo: <input type="file" name="file" size="25" />
     <input type="submit" name="submit" value="Submit" />
    </form>
  </div>
</div>

php

if(!$_FILES['file']['error'])
{
    $new_file_name = strtolower($_FILES['file']['tmp_name']); 
    $file_ext=strtolower(end(explode('.',$_FILES['file']['name'])));
    if($_FILES['file']['type'] !== 'text/html') 
    {
        $valid_file = false;
        $message = 'Oops!  Your file\'s not supported.';
        echo $message ;
    }

    else
    {
        $currentdir = getcwd();
        $target = $currentdir .'/uploads/' . basename($_FILES['file']['name']);
        $data = move_uploaded_file($_FILES['file']['tmp_name'], $target);       
        $contents = file_get_contents($target);
        echo '<div class="demo-wrapper html5-progress-bar">';
        echo '<div class="progress-bar-wrapper">';
        echo '<progress id="progressbar" value="0" max="100"></progress>';
        echo '<span class="progress-value">0%s</span>';
        echo '</div>';
        echo '</div>';  
        echo $contents;
    }
}