(PHP 4 >= 4.3.0, PHP 5)
stream_filter_append — Attach a filter to a stream
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.
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 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().
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_READ and STREAM_FILTER_WRITE to get both filter resources.