Create thumbnail from a multiple upload

Question

Good afternoon, already researched and tried several options and could not.

I’m trying to upload multiple images, and each image generates a thumbnail and record only the original images in the database. But it generates the Thumb of only one image or creates an image with all the names of the upload files, this gives when I change $novaImagem for $img for example:

tbn_1231455.jpg,tbn_3244545.jpg,tbn_8748545.jpg

I’m in need of help, below is my code.

if (isset($_FILES['imagemlocal']))
{       
   $largura = 1024;
   $altura = 1024;
   $tamanho =  200000;
   $tmp = $_FILES['imagemlocal'];
   list($largura,$altura,$tip)=getimagesize($tmp);
   $dimensoes = getimagesize($imagemlocal["tmp_name"]);

   $img = array();
   for ($key = 0; $key < count($tmp['name']); $key++) {
      $path = $_FILES['imagemlocal']['name'][$key];
      $ext = pathinfo($path, PATHINFO_EXTENSION);
      $temp_name = $_FILES['imagemlocal']['tmp_name'][$key];
      $novaImagem = md5(uniqid(time())) . "." . $ext;
      $caminho = 'img/'.$novaImagem;
      move_uploaded_file($temp_name, $caminho);
      $img[] = ("$novaImagem");
   }
   $img = implode(', ', $img);          
}

//thumb

if($tip > 1) {
   $percent = 0.15;
   $new_largura = $largura * $percent;
   $new_altura = $altura * $percent;

   $thundebal = imagecreatefromjpeg($caminho);
}
else {
   $thundebal = imagecreatefrompng($caminho);
}

$Thundeball = imagecreatetruecolor($new_largura, $new_altura);
imagecopyresampled($Thundeball, $thundebal, 0, 0, 0, 0, $new_largura, $new_altura, $largura, $altura);
if($tip > 1) {
    imagejpeg($Thundeball,"img/".'/tbn_'.$novaImagem);
}
else {
    imagepng($Thundeball,"img/".'/tbn_'.$novaImagem);
}