<?php

   if(isset($_FILES['arquivo']))
   {
      $arquivo = $_FILES['arquivo'];
      $caminho = 'C:/xampp/htdocs/upload/arquivos/' . $arquivo['name'];

      move_uploaded_file($arquivo['tmp_name'], $caminho);

   }

?>

<form name="upload" action="" enctype="multipart/form-data" method="post">
   <input type="file" name="arquivo" />
   <input type="submit" value="Enviar">
</form>