<?php

 /**

  * 引用：http://php.net/manual/en/function.stream-wrapper-register.php

  * 把变量当成文件读写的协议

  *

  * Class VariableStream

  */

 class VariableStream

 {

     private $postition;   // 当前的位置

     private $varname;     // 变量的名字

     /**

      * 打开

      *

      * @param $path

      * @param $mode

      * @param $options

      * @param $opened_path

      * @return bool

      */

     public function stream_open($path, $mode, $options, &$opened_path)

     {

         $url = parse_url($path);

         $this->varname   = $url['host'];

         $this->postition = 0;

         return true;

     }

     /**

      * 读取

      *

      * @param $count

      * @return string

      */

     public function stream_read($count)

     {

         $p   = $this->postition;

         $ret = substr($GLOBALS[$this->varname], $p,$count);

         $p  += $count;

         return $ret;

     }

     /**

      * 写入

      *

      * @param $data

      * @return int

      */

     public function stream_write($data)

     {

         $v = &$GLOBALS[$this->varname];

         $l = strlen($data);

         $p = &$this->postition;

         $v = substr($v,0,$p) .$data.substr($v,$p+=$l);

         return $l;

     }

     /**

      * 返回位置

      *

      * @return mixed

      */

     public function stream_tell()

     {

         return $this->postition;

     }

     /**

      * 寻位

      *

      * @param $offset

      * @param $whence

      * @return bool

      */

     public function stream_seek($offset, $whence)

     {

         $dp = $p = &$this->postition;

         $l  = strlen($GLOBALS[$this->varname]);

         switch($whence)

         {

             case SEEK_SET:

                 $p = 0;

                 break;

             case SEEK_END:

                 $p = $l;

                 break;

             default:

                 return false;

         }

         $p += $offset;

         $ret = ($p >= 0 || $p <= $l);

         if(!$ret)

             $this->postition = $dp;

         return $ret;

     }

     public function stream_eof()

     {

         return strlen($GLOBALS[$this->varname])== $this->postition;

     }

 }

 // 撤销已注册的同名协议

 if(in_array('var',stream_get_wrappers()))

 {

     stream_wrapper_unregister('var');

 }

 // 注册自己的协议

 stream_wrapper_register('var','VariableStream') or die('Failed to register protocol');

 $myvar = "";

 $fp = fopen('var://myvar','r+');

 if(!$fp){

     die('Failed to open the file!');

 }

 $str = "Hello the world!";

 fwrite($fp,$str,strlen($str));

 echo 'The length of the string is ' .strlen($myvar) ."\n";

 echo 'The value of variable ,$myvar,is :' .$myvar ."\n";

 echo 'The position of the cursor is :' .ftell($fp) ."\n";

 echo 'Is at the end of the file :' .(feof($fp) ? 'true':'false') ."\n";

 if(fseek($fp,-16,SEEK_END))

 {

     echo 'Now,the position is :' .ftell($fp);

 }