Adds filtername to the list of filters attached to stream. 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().
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:
+). The filter
will also be attached to the
write filter chain
if the file was opened for writing (i.e. File Mode:
STREAM_FILTER_ALL can also be passed to the
read_write parameter to override this behavior.
As of PHP 5.1.0, this function returns a resource which
can be used to refer to this filter instance during a call
Prior to PHP 5.1.0, this function returns
TRUE on success
FALSE on failure.
/* 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
stream_filter_register() must be called first in order to register the desired user filter to filtername.
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().