(PHP 4 >= 4.3.0, PHP 5, PHP 7)
stream_filter_append — Attach a filter to a stream
filtername to the list of filters
The target stream.
The filter name.
By default, stream_filter_append() 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_ALL can also be passed to the
read_write parameter to override this behavior.
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
Returns a resource on success or
FALSE on failure. The resource can be
used to refer to this filter instance during a call to
FALSE is returned if
stream is not a resource or
filtername cannot be located.
Prior to PHP 5.1.0, this function returns
Example #1 Controlling where filters are applied
/* 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\n");
/* Back up to the beginning of the file */
/* 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 */
/* Expected Output
Guvf vf n grfg
Note: When using custom (user) filters
stream_filter_register() must be called first in order to register the desired user filter to
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().
Note: When a filter is added for read and write, two instances of the filter are created. stream_filter_append() must be called twice with
STREAM_FILTER_WRITEto get both filter resources.