帮助理解魔术\u引号\u gpc()

我从一个上传文件的教程中学习了这个PHP代码

<form method="post" enctype="multipart/form-data">
  <input name="userfile" type="file" id="userfile">  
</form>

<?php
  if (isset($_POST['upload']) && $_FILES['userfile']['size'] > 0) {
    $fileName = $_FILES['userfile']['name'];
    $tmpName  = $_FILES['userfile']['tmp_name'];
    $fileSize = $_FILES['userfile']['size'];
    $fileType = $_FILES['userfile']['type'];

    $fp      = fopen($tmpName, 'r');
    $content = fread($fp, filesize($tmpName));
    $content = addslashes($content);
    fclose($fp);

   if (!get_magic_quotes_gpc()) {
     $fileName = addslashes($fileName);
   }

   include 'library/config.php';
   include 'library/opendb.php';

   $query = "INSERT INTO upload (name, size, type, content ) ".
     "VALUES ('$fileName', '$fileSize', '$fileType', '$content')";

   mysql_query($query) or die('Error, query failed');
   include 'library/closedb.php';

现在我通过使用php文档了解了每个函数和所有内容

除外

get_magic_quotes_gpc()

• 它是什么?它是干什么的?
• PHP手册中说:“从PHP5.3.0开始,这个特性就被弃用了。不鼓励依赖此功能。“。请详细说明?
• 有没有办法上传文件到(网络)服务器硬盘,并提供链接到他们。。