stream_filter_append

Description

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: 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.

As of PHP 5.1.0, this function returns a resource which can be used to refer to this filter instance during a call to stream_filter_remove(). Prior to PHP 5.1.0, this function returns TRUE on success or FALSE on failure.

<?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\n");

/* 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

 */
?>

See also stream_filter_register(), stream_filter_prepend(), and stream_get_filters().