Description
bool
stream_filter_register ( string filtername, string classname )
stream_filter_register() allows you to implement
your own filter on any registered stream used with all the other
filesystem functions (such as fopen(),
fread() etc.).
To implement a filter, you need to define a class as an extension of
php_user_filter with a number of member functions
as defined below. When performing read/write operations on the stream
to which your filter is attached, PHP will pass the data through your
filter (and any other filters attached to that stream) so that the
data may be modified as desired. You must implement the methods
exactly as described below - doing otherwise will lead to undefined
behaviour.
stream_filter_register() will return FALSE if the
filtername is already defined.
int
filter ( resource in, resource out, int &consumed, bool closing )
This method is called whenever data is read from or written to
the attached stream (such as with fread() or fwrite()).
in is a resource pointing to a bucket brigade
which contains one or more bucket objects containing data to be filtered.
out is a resource pointing to a second bucket brigade
into which your modified buckets should be placed.
consumed, which must always
be declared by reference, should be incremented by the length of the data
which your filter reads in and alters. In most cases this means you will
increment consumed by $bucket->datalen for each $bucket.
If the stream is in the process of closing (and therefore this is the last pass
through the filterchain), the closing parameter will be
set to TRUE The filter method must return one of
three values upon completion.
bool
onCreate ( void )
This method is called during instantiation of the filter class
object. If your filter allocates or initializes any other resources
(such as a buffer), this is the place to do it. Your implementation of
this method should return FALSE on failure, or TRUE on success.
When your filter is first instantiated, and
yourfilter->onCreate() is called, a number of properties
will be available as shown in the table below.
void
onClose ( void )
This method is called upon filter shutdown (typically, this is also
during stream shutdown), and is executed after
the flush method is called. If any resources
were allocated or initialzed during onCreate
this would be the time to destroy or dispose of them.
The example below implements a filter named strtoupper
on the foo-bar.txt stream which will capitalize
all letter characters written to/read from that stream.
Example 1. Filter for capitalizing characters on foo-bar.txt stream
<?php
/* Define our filter class */
class strtoupper_filter extends php_user_filter {
function filter($in, $out, &$consumed, $closing)
{
while ($bucket = stream_bucket_make_writeable($in)) {
$bucket->data = strtoupper($bucket->data);
$consumed += $bucket->datalen;
stream_bucket_append($out, $bucket);
}
return PSFS_PASS_ON;
}
}
/* Register our filter with PHP */
stream_filter_register("strtoupper", "strtoupper_filter")
or die("Failed to register filter");
$fp = fopen("foo-bar.txt", "w");
/* Attach the registered filter to the stream just opened */
stream_filter_append($fp, "strtoupper");
fwrite($fp, "Line1\n");
fwrite($fp, "Word - 2\n");
fwrite($fp, "Easy As 123\n");
fclose($fp);
/* Read the contents back out
*/
readfile("foo-bar.txt");
?>
|
The above example will output: LINE1
WORD - 2
EASY AS 123 |
|
Example 2. Registering a generic filter class to match multiple filter names.
<?php
/* Define our filter class */
class string_filter extends php_user_filter {
var $mode;
function filter($in, $out, &$consumed, $closing)
{
while ($bucket = stream_bucket_make_writeable($in)) {
if ($this->mode == 1) {
$bucket->data = strtoupper($bucket->data);
} elseif ($this->mode == 0) {
$bucket->data = strtolower($bucket->data);
}
$consumed += $bucket->datalen;
stream_bucket_append($out, $bucket);
}
return PSFS_PASS_ON;
}
function onCreate()
{
if ($this->filtername == 'str.toupper') {
$this->mode = 1;
} elseif ($this->filtername == 'str.tolower') {
$this->mode = 0;
} else {
/* Some other str.* filter was asked for,
report failure so that PHP will keep looking */
return false;
}
return true;
}
}
/* Register our filter with PHP */
stream_filter_register("str.*", "string_filter")
or die("Failed to register filter");
$fp = fopen("foo-bar.txt", "w");
/* Attach the registered filter to the stream just opened
We could alternately bind to str.tolower here */
stream_filter_append($fp, "str.toupper");
fwrite($fp, "Line1\n");
fwrite($fp, "Word - 2\n");
fwrite($fp, "Easy As 123\n");
fclose($fp);
/* Read the contents back out
*/
readfile("foo-bar.txt");
?>
|
The above example will output: LINE1
WORD - 2
EASY AS 123 |
|
See also
stream_wrapper_register(),
stream_filter_prepend(), and
stream_filter_append().
