WeberDev.com -> PHP Manual -> Register a URL wrapper implemented as a PHP class

Description

bool stream_wrapper_register ( string $protocol , string $classname )

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

To implement a wrapper, you need to define a class with a number of member functions, as defined below. When someone fopens your stream, PHP will create an instance of classname and then call methods on that instance. You must implement the methods exactly as described below - doing otherwise will lead to undefined behaviour.

Note: As of PHP 5.0.0 the instance of classname will be populated with a context property referencing a Context Resource which may be accessed with stream_context_get_options(). If no context was passed to the stream creation function, context will be set to NULL.

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

bool stream_open ( string $path , string $mode , int $options , string $opened_path )

This method is called immediately after your stream object is created. path specifies the URL that was passed to fopen() and that this object is expected to retrieve. You can use parse_url() to break it apart.

mode is the mode used to open the file, as detailed for fopen(). You are responsible for checking that mode is valid for the path requested.

options holds additional flags set by the streams API. It can hold one or more of the following values OR'd together.

Flag	Description
STREAM_USE_PATH	If `path` is relative, search for the resource using the include_path.
STREAM_REPORT_ERRORS	If this flag is set, you are responsible for raising errors using trigger_error() during opening of the stream. If this flag is not set, you should not raise any errors.

If the path is opened successfully, and STREAM_USE_PATH is set in options , you should set opened_path to the full path of the file/resource that was actually opened.

If the requested resource was opened successfully, you should return TRUE, otherwise you should return FALSE

void stream_close ( void )

This method is called when the stream is closed, using fclose(). You must release any resources that were locked or allocated by the stream.

string stream_read ( int $count )

This method is called in response to fread() and fgets() calls on the stream. You must return up-to count bytes of data from the current read/write position as a string. If there are less than count bytes available, return as many as are available. If no more data is available, return either FALSE or an empty string. You must also update the read/write position of the stream by the number of bytes that were successfully read.

int stream_write ( string $data )

This method is called in response to fwrite() calls on the stream. You should store data into the underlying storage used by your stream. If there is not enough room, try to store as many bytes as possible. You should return the number of bytes that were successfully stored in the stream, or 0 if none could be stored. You must also update the read/write position of the stream by the number of bytes that were successfully written.

bool stream_eof ( void )

This method is called in response to feof() calls on the stream. You should return TRUE if the read/write position is at the end of the stream and if no more data is available to be read, or FALSE otherwise.

int stream_tell ( void )

This method is called in response to ftell() calls on the stream. You should return the current read/write position of the stream.

bool stream_seek ( int $offset , int $whence )

This method is called in response to fseek() calls on the stream. You should update the read/write position of the stream according to offset and whence . See fseek() for more information about these parameters. Return TRUE if the position was updated, FALSE otherwise.

bool stream_flush ( void )

This method is called in response to fflush() calls on the stream. If you have cached data in your stream but not yet stored it into the underlying storage, you should do so now. Return TRUE if the cached data was successfully stored (or if there was no data to store), or FALSE if the data could not be stored.

array stream_stat ( void )

This method is called in response to fstat() calls on the stream and should return an array containing the same values as appropriate for the stream.

resource stream_cast ( int $cast_as )

This method is called in response to stream_select() calls on the stream and should return the underlying stream resource used by the wrapper, or FALSE. The cast_as parameter can be STREAM_CAST_FOR_SELECT when stream_select() is calling stream_cast() or STREAM_CAST_AS_STREAM when stream_cast() is called for other uses.

Note: Userspace wrapper stream_cast method is not supported prior to PHP 5.3.0.

bool stream_set_option ( int $option , int $arg1 , int $arg2 )

This method is called to set options on the stream. Possible values for option are:

STREAM_OPTION_BLOCKING: The method is called in response to stream_set_blocking(). arg1 is the requested blocking mode.
STREAM_OPTION_READ_TIMEOUT: The method is called in response to stream_set_timeout(). arg1 is the timeout in seconds, and arg2 is the timeout in microseconds.
STREAM_OPTION_WRITE_BUFFER: The method is called in response to stream_set_write_buffer(). arg1 is the buffer mode (STREAM_BUFFER_NONE or STREAM_BUFFER_FULL) and arg2 is the requested buffer size.

stream_set_option() should return FALSE on failure or if the option is not implemented, TRUE otherwise.

Note: Userspace wrapper stream_set_option method is not supported prior to PHP 5.3.0.

bool unlink ( string $path )

This method is called in response to unlink() calls on URL paths associated with the wrapper and should attempt to delete the item specified by path . It should return TRUE on success or FALSE on failure. In order for the appropriate error message to be returned, do not define this method if your wrapper does not support unlinking.

Note: Userspace wrapper unlink method is not supported prior to PHP 5.0.0.

bool rename ( string $path_from , string $path_to )

This method is called in response to rename() calls on URL paths associated with the wrapper and should attempt to rename the item specified by path_from to the specification given by path_to . It should return TRUE on success or FALSE on failure. In order for the appropriate error message to be returned, do not define this method if your wrapper does not support renaming.

Note: Userspace wrapper rename method is not supported prior to PHP 5.0.0.

bool mkdir ( string $path , int $mode , int $options )

This method is called in response to mkdir() calls on URL paths associated with the wrapper and should attempt to create the directory specified by path . It should return TRUE on success or FALSE on failure. In order for the appropriate error message to be returned, do not define this method if your wrapper does not support creating directories. Posible values for options include STREAM_REPORT_ERRORS and STREAM_MKDIR_RECURSIVE.

Note: Userspace wrapper mkdir method is not supported prior to PHP 5.0.0.

bool rmdir ( string $path , int $options )

This method is called in response to rmdir() calls on URL paths associated with the wrapper and should attempt to remove the directory specified by path . It should return TRUE on success or FALSE on failure. In order for the appropriate error message to be returned, do not define this method if your wrapper does not support removing directories. Possible values for options include STREAM_REPORT_ERRORS.

Note: Userspace wrapper rmdir method is not supported prior to PHP 5.0.0.

bool dir_opendir ( string $path , int $options )

This method is called immediately when your stream object is created for examining directory contents with opendir(). path specifies the URL that was passed to opendir() and that this object is expected to explore. You can use parse_url() to break it apart.

array url_stat ( string $path , int $flags )

This method is called in response to stat() calls on the URL paths associated with the wrapper and should return as many elements in common with the system function as possible. Unknown or unavailable values should be set to a rational value (usually 0).

flags holds additional flags set by the streams API. It can hold one or more of the following values OR'd together.

Flag	Description
STREAM_URL_STAT_LINK	For resources with the ability to link to other resource (such as an HTTP Location: forward, or a filesystem symlink). This flag specified that only information about the link itself should be returned, not the resource pointed to by the link. This flag is set in response to calls to lstat(), is_link(), or filetype().
STREAM_URL_STAT_QUIET	If this flag is set, your wrapper should not raise any errors. If this flag is not set, you are responsible for reporting errors using the trigger_error() function during stating of the path.

string dir_readdir ( void )

This method is called in response to readdir() and should return a string representing the next filename in the location opened by dir_opendir().

bool dir_rewinddir ( void )

This method is called in response to rewinddir() and should reset the output generated by dir_readdir(). i.e.: The next call to dir_readdir() should return the first entry in the location returned by dir_opendir().

bool dir_closedir ( void )

This method is called in response to closedir(). You should release any resources which were locked or allocated during the opening and use of the directory stream.

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;
        }
    }
}

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);

?>

stream_wrapper_register

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