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PHP : Function Reference : Stream Functions : stream_filter_append

stream_filter_append

Attach a filter to a stream (PHP 4 >= 4.3.0, PHP 5)
resource stream_filter_append ( resource stream, string filtername [, int read_write [, mixed params]] )

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 2374. 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\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

*/
?>


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().

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

Related Examples ( Source code ) » stream_filter_append


Code Examples / Notes » stream_filter_append

net_navard

Hello firends
The difference betweem adding a stream filter first or last in the filte list in only the order they will be applied to streams.
For example, if you're reading data from a file, and a given filter is placed in first place with stream_filter_prepend()the data will be processed by that filter first.
This example reads out file data and the filter is applied at the beginning of the reading operation:
<?php
/* Open a test file for reading */
$fp = fopen("test.txt", "r");
/* Apply the ROT13 filter to the
* read filter chain, but not the
* write filter chain */
stream_filter_prepend($fp, "string.rot13",
STREAM_FILTER_READ);
// read file data
$contents=fread($fp,1024);
// file data is first filtered and stored in $contents
echo $contents;
fclose($fp);
?>
On the other hand, if stream_filter_append() is used, then the filter will be applied at the end of the data operation. The thing about this is only the order filters are applied to streams. Back to the example, it's not the same thing removing new lines from file data and then counting the number of characters, than performing the inverse process. In this case, the order that filters are applied to stream is important.
This example writes a test string to a file. The filter is applied at the end of the writing operation:
<?php
/* Open a test file for 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 at the end of the
stream operation
* way out */
fwrite($fp, "This is a test\n"); // string data is
first written, then ROT13 tranformed and lastly
written to file
/* Back up to the beginning of the file */
rewind($fp);
$contents=fread($fp,512);
fclose($fp);
echo $contents;
?>
In the first case, data is transformed at the end of the writing operation, while in the second one, data is first filtered and then stored in $contents.
                         With Regards
                             Hossein


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stream_bucket_append
stream_bucket_make_writeable
stream_bucket_new
stream_bucket_prepend
stream_context_create
stream_context_get_default
stream_context_get_options
stream_context_set_option
stream_context_set_params
stream_copy_to_stream
stream_encoding
stream_filter_append
stream_filter_prepend
stream_filter_register
stream_filter_remove
stream_get_contents
stream_get_filters
stream_get_line
stream_get_meta_data
stream_get_transports
stream_get_wrappers
stream_register_wrapper
stream_resolve_include_path
stream_select
stream_set_blocking
stream_set_timeout
stream_set_write_buffer
stream_socket_accept
stream_socket_client
stream_socket_enable_crypto
stream_socket_get_name
stream_socket_pair
stream_socket_recvfrom
stream_socket_sendto
stream_socket_server
stream_socket_shutdown
stream_wrapper_register
stream_wrapper_restore
stream_wrapper_unregister
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