5.5.15

stream_wrapper_register

(PHP 4 >= 4.3.2, PHP 5)

stream_wrapper_registerRegister a URL wrapper implemented as a PHP class

Beschreibung

bool stream_wrapper_register ( string $protocol , string $classname [, int $flags = 0 ] )

Allows you to implement your own protocol handlers and streams for use with all the other filesystem functions (such as fopen(), fread() etc.).

Parameter-Liste

protocol

The wrapper name to be registered.

classname

The classname which implements the protocol.

flags

Should be set to STREAM_IS_URL if protocol is a URL protocol. Default is 0, local stream.

Rückgabewerte

Gibt bei Erfolg TRUE zurück. Im Fehlerfall wird FALSE zurückgegeben.

stream_wrapper_register() will return FALSE if the protocol already has a handler.

Changelog

Version Beschreibung
5.2.4 Added the flags parameter.

Beispiele

Beispiel #1 How to register a stream wrapper

<?php
$existed 
in_array("var"stream_get_wrappers());
if (
$existed) {
    
stream_wrapper_unregister("var");
}
stream_wrapper_register("var""VariableStream");
$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);

if (
$existed) {
    
stream_wrapper_restore("var");
}

?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

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

Siehe auch

add a note add a note

User Contributed Notes 13 notes

up
4
fordiman at gmail dot com
6 years ago
Updated for PHP 5, and optimized for readability, low line count, and minimum memory use:

<?php
class VariableStream {
    private
$position;
    private
$varname;
    public function
stream_open($path, $mode, $options, &$opened_path) {
       
$url = parse_url($path);
       
$this->varname = $url["host"];
       
$this->position = 0;
        return
true;
    }
    public function
stream_read($count) {
       
$p=&$this->position;
       
$ret = substr($GLOBALS[$this->varname], $p, $count);
       
$p += strlen($ret);
        return
$ret;
    }
    public function
stream_write($data){
       
$v=&$GLOBALS[$this->varname];
       
$l=strlen($data);
       
$p=&$this->position;
       
$v = substr($v, 0, $p) . $data . substr($v, $p += $l);
        return
$l;
    }
    public function
stream_tell() {
        return
$this->position;
    }
    public function
stream_eof() {
        return
$this->position >= strlen($GLOBALS[$this->varname]);
    }
    public function
stream_seek($offset, $whence) {
       
$l=strlen(&$GLOBALS[$this->varname]);
       
$p=&$this->position;
        switch (
$whence) {
            case
SEEK_SET: $newPos = $offset; break;
            case
SEEK_CUR: $newPos = $p + $offset; break;
            case
SEEK_END: $newPos = $l + $offset; break;
            default: return
false;
        }
       
$ret = ($newPos >=0 && $newPos <=$l);
        if (
$ret) $p=$newPos;
        return
$ret;
    }
}
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);
?>
up
2
Anonymouse at Coward dot com
7 years ago
Use caution with writing code that may use stream wrappers with fread, as fread behaviour is 'inconsistent' with normal file operations because of the 8192 bytes internal buffer used by PHP ( >= 5.0.5 IIRC ).

ie:

fread($filehandle, filesize($filename))

will not work correctly if the file is larger than 8KB, it will only get you the first 8192 bytes. Also, it seems that:

fread($filehandle, 4096)

will still give you 8KB (if the file is larger than 8KB) as 8192 bytes is always passed to stream_read as count.

This makes it somewhat impossible to just 'drop in' a stream where normally a file would be used without taking special care.

Yes, it IS mentioned in the documentation here if you read it really well, but I for one spent some time scratching my head over it, and looking at the bug tracker, I am not the only one. The dev's say this inconsistancy is a feature though, even if it does make stream wrappers pretty much useless 'out of the box'.

file_get_contents and stream_get_contents seem to work ok though.
up
2
cellog at php dot net
9 years ago
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!
up
1
Anonymous
5 years ago
"for use with all the other filesystem functions"

"all" is not accurate.  Unfortunately, zip_open(), and presumably others, will ignore your custom stream wrapper.
up
0
dmarjos at gmail dot com
10 months ago
Be aware that even when stream_wrapper_register won't fail, open_basedir will affect functionality of the class.
up
0
phrank
6 years ago
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;
    }
up
0
yeiniel at gmail dot com
6 years ago
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
  }
}
up
0
fordiman at gmail dot com
6 years ago
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://.
<?php
class GlobalStream {
    private
$pos;
    private
$stream;
    public function
stream_open($path, $mode, $options, &$opened_path) {
       
$url = parse_url($path);
       
$this->stream = &$GLOBALS[$url["host"]];
       
$this->pos = 0;
        if (!
is_string($this->stream)) return false;
        return
true;
    }
    public function
stream_read($count) {
       
$p=&$this->pos;
       
$ret = substr($this->stream, $this->pos, $count);
       
$this->pos += strlen($ret);
        return
$ret;
    }
    public function
stream_write($data){
       
$l=strlen($data);
       
$this->stream =
           
substr($this->stream, 0, $this->pos) .
           
$data .
           
substr($this->stream, $this->pos += $l);
        return
$l;
    }
    public function
stream_tell() {
        return
$this->pos;
    }
    public function
stream_eof() {
        return
$this->pos >= strlen($this->stream);
    }
    public function
stream_seek($offset, $whence) {
       
$l=strlen($this->stream);
        switch (
$whence) {
            case
SEEK_SET: $newPos = $offset; break;
            case
SEEK_CUR: $newPos = $this->pos + $offset; break;
            case
SEEK_END: $newPos = $l + $offset; break;
            default: return
false;
        }
       
$ret = ($newPos >=0 && $newPos <=$l);
        if (
$ret) $this->pos=$newPos;
        return
$ret;
    }
}
stream_wrapper_register('global', 'GlobalStream') or die('Failed to register protocol global://');

$myvar = "";
  
$fp = fopen("global://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);
?>
up
0
phpnet at povaddict dot com dot ar
7 years ago
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.

<?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)
    {
        echo
"stream_read called asking for $count bytes\n";
       
$ret = substr($GLOBALS[$this->varname], $this->position, $count);
       
$this->position += strlen($ret);
        return
$ret;
    }

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

}

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

$myvar = "";
$l=range('a','z');
for(
$i=0;$i<65536;$i++) {
   
$myvar .= $l[array_rand($l)];
}
  
$fp = fopen("var://myvar", "r+");

while (!
feof($fp)) {
   
$out = fread($fp,1000);
    echo
"fread returned ",strlen($out)," bytes\n";
}

fclose($fp);

?>
up
0
none at your dot biz
7 years ago
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','<'))
        {
            $eof = !$eof;
        }
        return $eof;
   }

PHP 5.0 introduced a bug that wasn't fixed until 5.1
up
0
Hayley Watson
9 years ago
The current URL standard is RFC 3986 - available at www.ietf.org/rfc/rfc3986.txt
up
0
simon at firepages dot org
10 years ago
using streams to use the ever useful fgetcsv() on a variable where explode() would not work (and would otherwise require regex(though that may be easier;)))

$explode_this="yak, llama, 'big llama', 'wobmat, with a comma in it', bandycoot";

<?php
class csvstream{
   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_eof(){ 
       return
$this->position >= strlen($GLOBALS[$this->varname]); 
   } 
   function
stream_tell(){ 
       return
$this->position
   } 
}

  
stream_wrapper_register("csvstr", "csvstream") ;
  
$str="yak, llama, 'big llama', 'wobmat, with a comma in it', bandycoot";

  
$fp = fopen("csvstr://str", "r+"); 
  
print_r(fgetcsv($fp,100,",","'"));

?>
up
-1
jhannus at php dot net
9 years ago
It is worth noting that if your wrapper supports stream_flush() then when you flcose() your stream this function will be called prior to closing the stream.
To Top