stream_wrapper_register()

(PHP 4 >= 4.3.2, PHP 5, PHP 7)

注册一个用 PHP 类实现的 URL 封装协议

说明

允许用户实现自定义的协议处理器和流，用于所有其它的文件系统函数中（例如fopen()，fread()等）。

参数

待注册的封装的名字。

实现了$protocol的类名。

Should be set toSTREAM_IS_URLif$protocolis a URL protocol. Default is 0, local stream.

返回值

成功时返回TRUE，或者在失败时返回FALSE。

当$protocol已经有处理者时，stream_wrapper_register()将返回FALSE

更新日志

范例

如何注册一个 stream wrapper

以上例程会输出：

line1
line2
line3
string(18) "line1
line2
line3
"

参见

• ThestreamWrapperprototype class
• Example class registered as stream wrapper
• stream_wrapper_unregister()Unregister a URL wrapper
• stream_wrapper_restore()Restores a previously unregistered built-in wrapper
• stream_get_wrappers() 获取已注册的流类型

If you plan to use your wrapper in a require_once you need to define stream_stat(). If you plan to allow any other tests like is_file()/is_dir(), you have to define url_stat().
stream_stat() must define the size of the file, or it will never be included. url_stat() must define mode, or is_file()/is_dir()/is_executable(), and any of those functions affected by clearstatcache() simply won't work.
It's not documented, but directories must be a mode like 040777 (octal), and files a mode like 0100666. If you wish the file to be executable, use 7s instead of 6s. The last 3 digits are exactly the same thing as what you pass to chmod. 040000 defines a directory, and 0100000 defines a file. It would be really helpful to add this to the official manual!

Updated for PHP 5, and optimized for readability, low line count, and minimum memory use: 

In response to Anonymouse at Coward dot com:
The manual says "Reading stops when up to length bytes have been read, [...] or (after opening userspace stream) when 8192 bytes have been read whichever comes first."
I tested it and fread($filehandle, 4096) returns 4096 bytes, so it's working as the manual says it should. You're right when you say "8192 bytes is always passed to stream_read as count", but that doesn't mean fread will return 8192 bytes. If you call fread twice with length 4096, PHP calls stream_read passing 8192 as count on the first fread, and doesn't call it on second fread. On both cases, fread returns the correct amount of bytes. 

Actually, I don't know if there's a better way to figure out if stream_read() was called by fgets() or e.g. fread() than this one:
  public function stream_read($count)
  {
    $bt = debug_backtrace();
    if(($bt[0]['function'] == 'stream_read') &&
      ($bt[1]['function'] == 'fgets'))
    {
        $pos = strpos($GLOBALS[$this->varname], "\n", $this->position);
        $retval = substr($GLOBALS[$this->varname], $this->position, ($pos > $count) ? $count : $pos+1);
    }
    else
    {
        $retval = substr($GLOBALS[$this->varname], $this->position, $count);
    }
        $this->position += strlen($retval);
        return (string)$retval;
  }

on using dir_opendir on PHP5 make sure you not return a resource object on success. A resource object is diferent from false but php make a cast to bool to dir_opendir return value and modify the value of your resource to 1. 
example:
class myclass{
 private $mysqlHandler;
 public function dir_opendir(....)
 {
  $this->mysqlHandler = mysql_connect(....);
  return $this->mysqlHandler; //this is wrong, next
                     //time you use 
                     //$this->mysqlHandler
                     // the value is 1
 }
}

Updated. I figured there's no need to store the variable name if we're dereferenceing; we can just store the pointer and not have to dereference in each function for brevity.
Also, I added the assertion that the stream is a string, since we're behaving basically like it has to be, and I changed the name to GlobalStream and global://, as that's a more descriptive moniker than VariableName/var://. 

Be aware that even when stream_wrapper_register won't fail, open_basedir will affect functionality of the class.

"for use with all the other filesystem functions"
"all" is not accurate. Unfortunately, zip_open(), and presumably others, will ignore your custom stream wrapper.

In case someone else starts scratching their head like I was, you should change the VariableStream::stream_eof() function to something like this:
  function stream_eof()
  {
    $eof = ($this->position >= strlen($GLOBALS[$this->varname]));
    if(version_compare(PHP_VERSION,'5.0','>=') && version_compare(PHP_VERSION,'5.1','

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