PHP で特定の名前を付けてファイルをアップロードして保存するにはどうすればよいですか?

<form action="" method="POST" enctype="multipart/form-data">
  <input type="file" name="userFile"><br>
  <input type="submit" name="upload_btn" value="upload">
</form>

<?php
$target_Path = "images/";
$target_Path .= basename($_FILES['userFile']['name']);
move_uploaded_file($_FILES['userFile']['tmp_name'], $target_Path);
?>

$info = pathinfo($_FILES['userFile']['name']);
$ext = $info['extension']; // get the extension of the file
$newname = "desired_filename.".$ext;

$target = 'images/'.$newname;
move_uploaded_file($_FILES['userFile']['tmp_name'], $target);