stream_register_filter

Description

bool stream_register_filter ( string filtername, string classname)

stream_register_filter() 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_fitler with a number of member functions as defined below. When performing read/write opperations 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_register_filter() will return FALSE if the filtername is already defined.

int filter ( resource in, resource out, int &consumed, boolean 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 indicates success with data available in the out bucket brigade. PSFS_FEED_ME indicates that the filter has no data available to return and requires additional data from the stream. PSFS_ERR_FATAL indicates that the filter experienced an unrecoverable error and cannot continue. If no value is returned by this method, PSFS_ERR_FATAL will be assumed.

void 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.

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.

Пример 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_register_filter("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"); /* Output * ------ LINE1 WORD - 2 EASY AS 123 */ ?>

See Also: stream_register_wrapper(), stream_filter_prepend(), and stream_filter_append()