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Example class registered as stream wrapper


Example class registered as stream wrapper

The example below implements a var:// protocol handler that allows read/write access to a named global variable using standard filesystem stream functions such as fread(). The var:// protocol implemented below, given the URL "var://foo" will read/write data to/from $GLOBALS["foo"].

Example #1 A Stream for reading/writing global variables

<?php

class VariableStream {
    var 
$position;
    var 
$varname;

    function 
stream_open($path$mode$options, &$opened_path)
    {
        
$url parse_url($path);
        
$this->varname $url["host"];
        
$this->position 0;

        return 
true;
    }

    function 
stream_read($count)
    {
        
$ret substr($GLOBALS[$this->varname], $this->position$count);
        
$this->position += strlen($ret);
        return 
$ret;
    }

    function 
stream_write($data)
    {
        
$left substr($GLOBALS[$this->varname], 0$this->position);
        
$right substr($GLOBALS[$this->varname], $this->position strlen($data));
        
$GLOBALS[$this->varname] = $left $data $right;
        
$this->position += strlen($data);
        return 
strlen($data);
    }

    function 
stream_tell()
    {
        return 
$this->position;
    }

    function 
stream_eof()
    {
        return 
$this->position >= strlen($GLOBALS[$this->varname]);
    }

    function 
stream_seek($offset$whence)
    {
        switch (
$whence) {
            case 
SEEK_SET:
                if (
$offset strlen($GLOBALS[$this->varname]) && $offset >= 0) {
                     
$this->position $offset;
                     return 
true;
                } else {
                     return 
false;
                }
                break;

            case 
SEEK_CUR:
                if (
$offset >= 0) {
                     
$this->position += $offset;
                     return 
true;
                } else {
                     return 
false;
                }
                break;

            case 
SEEK_END:
                if (
strlen($GLOBALS[$this->varname]) + $offset >= 0) {
                     
$this->position strlen($GLOBALS[$this->varname]) + $offset;
                     return 
true;
                } else {
                     return 
false;
                }
                break;

            default:
                return 
false;
        }
    }

    function 
stream_metadata($path$option$var
    {
        if(
$option == STREAM_META_TOUCH) {
            
$url parse_url($path);
            
$varname $url["host"];
            if(!isset(
$GLOBALS[$varname])) {
                
$GLOBALS[$varname] = '';
            }
            return 
true;
        }
        return 
false;
    }
}

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

$myvar "";

$fp fopen("var://myvar""r+");

fwrite($fp"line1\n");
fwrite($fp"line2\n");
fwrite($fp"line3\n");

rewind($fp);
while (!
feof($fp)) {
    echo 
fgets($fp);
}
fclose($fp);
var_dump($myvar);

?>

The above example will output:

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



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