STREAM_FILTER_APPEND(3) 1 STREAM_FILTER_APPEND(3)
stream_filter_append - Attach a filter to a stream
SYNOPSIS
resource stream_filter_append (resource $stream, string $filtername, [int $read_write], [mixed $params])
DESCRIPTION
Adds $filtername to the list of filters attached to $stream.
PARAMETERS
o $stream
- The target stream.
o $filtername
- The filter name.
o $read_write
- By default, stream_filter_append(3) will attach the filter to the read filter chain if the file was opened for reading (i.e.
File Mode: r, and/or +). The filter will also be attached to the write filter chain if the file was opened for writing (i.e. File
Mode: w, a, and/or +). STREAM_FILTER_READ, STREAM_FILTER_WRITE, and/or STREAM_FILTER_ALL can also be passed to the $read_write
parameter to override this behavior.
o $params
- This filter will be added with the specified $params to the end of the list and will therefore be called last during stream
operations. To add a filter to the beginning of the list, use stream_filter_prepend(3).
RETURN VALUES
Returns a resource which can be used to refer to this filter instance during a call to stream_filter_remove(3).
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.1.0 | |
| | |
| | Prior to PHP 5.1.0, this function returns TRUE |
| | on success or FALSE on failure. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
Controlling where filters are applied
<?php
/* Open a test file for reading and writing */
$fp = fopen('test.txt', 'w+');
/* Apply the ROT13 filter to the
* write filter chain, but not the
* read filter chain */
stream_filter_append($fp, "string.rot13", STREAM_FILTER_WRITE);
/* Write a simple string to the file
* it will be ROT13 transformed on the
* way out */
fwrite($fp, "This is a test
");
/* Back up to the beginning of the file */
rewind($fp);
/* Read the contents of the file back out.
* Had the filter been applied to the
* read filter chain as well, we would see
* the text ROT13ed back to its original state */
fpassthru($fp);
fclose($fp);
/* Expected Output
---------------
Guvf vf n grfg
*/
?>
NOTES
Note
When using custom (user) filters
stream_filter_register(3) must be called first in order to register the desired user filter to $filtername.
Note
Stream data is read from resources (both local and remote) in chunks, with any unconsumed data kept in internal buffers. When a new
filter is appended to a stream, data in the internal buffers is processed through the new filter at that time. This differs from the
behavior of stream_filter_prepend(3).
Note
When a filter is added for read and write, two instances of the filter are created. stream_filter_append(3) must be called twice
with STREAM_FILTER_READ and STREAM_FILTER_WRITE to get both filter resources.
SEE ALSO
stream_filter_register(3), stream_filter_prepend(3), stream_get_filters(3).
PHP Documentation Group STREAM_FILTER_APPEND(3)