(PHP 5)stream_filter_register -- Register a stream filter implemented as a PHP class derived from php_user_filter
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.
|PSFS_PASS_ON||Filter processed successfully with data available in the out bucket brigade.|
|PSFS_FEED_ME||Filter processed successfully, however no data was available to return. More data is required from the stream or prior filter.|
|PSFS_ERR_FATAL (default)||The filter experienced an unrecoverable error and cannot continue.|
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.
|FilterClass->filtername||A string containing the name the filter was instantiated with. Filters may be registered under multiple names or under wildcards. Use this property to determine which name was used.|
|FilterClass->params||The contents of the params parameter passed to stream_filter_append() or stream_filter_prepend().|
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.
Esempio 1. Filter for capitalizing characters on foo-bar.txt stream
Esempio 2. Registering a generic filter class to match multiple filter names.