stream_filter_register()

stream_filter_register() — Register a user defined stream filter.

Built-in function of PHP 8.5. The manual lists it as available in PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.

What it does

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.).

Signature

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

Parameters

Parameter	Type	What it takes
$filter_name	string	The filter name to be registered.
$class	string	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 - ...

Return value

Returns true on success or false on failure. stream_filter_register() will return false if the filter_name is already defined.

Example

A runnable snippet:

/* 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");

Output:

LINE1 WORD - 2 EASY AS 123