stream_filter_register

(PHP 5, PHP 7, PHP 8)

stream_filter_register — Register a user defined stream filter

Description

stream_filter_register(string$filter_name, string$class): bool

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.).

Parameters

filter_name: The filter name to be registered.
class: To implement a filter, you need to define a class as an extension of php_user_filter with a number of member functions. 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 in php_user_filter - doing otherwise will lead to undefined behaviour.

Return Values

Returns true on success or false on failure.

stream_filter_register() will return false if the filter_name is already defined.

Examples

Example #1 Filter for capitalizing characters on foo-bar.txt stream

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.

<?php


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;
 }
}


stream_filter_register("strtoupper", "strtoupper_filter")
 or die("Failed to register filter");

$fp = fopen("foo-bar.txt", "w");


stream_filter_append($fp, "strtoupper");

fwrite($fp, "Line1\n");
fwrite($fp, "Word - 2\n");
fwrite($fp, "Easy As 123\n");

fclose($fp);


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


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 {

return false;
 }

 return true;
 }
}


stream_filter_register("str.*", "string_filter")
 or die("Failed to register filter");

$fp = fopen("foo-bar.txt", "w");


stream_filter_append($fp, "str.toupper");

fwrite($fp, "Line1\n");
fwrite($fp, "Word - 2\n");
fwrite($fp, "Easy As 123\n");

fclose($fp);


readfile("foo-bar.txt");
?>