ZEND PHP 5 Certification STUDY GUIDE

250 ” Streams and Network Programming
are organized in a chain—thus, you can set them up so that the data passes through
multiple filters, sequentially.
You can add a filter to a stream by using stream_filter_prepend() and
stream_filter_append()—which, as you might guess, add a filter to the beginning
and end of the filter chain respectively:
$socket = stream_socket_server("tcp://0.0.0.0:1037");
while ($conn = stream_socket_accept($socket)) {
stream_filter_append($conn, ’string.toupper’);
stream_filter_append($conn, ’zlib.deflate’);
fwrite($conn, "Hello World\n");
fclose($conn);
}
fclose($socket);
In this example, we apply the string.toupper filter to our server stream, which will
convert the data to upper case, followed by the zlib.deflate filter to compress it
whenever we write data to it.
We can then apply the zlib.inflate filter to the client, and complete the implementation
of a compressed data stream between server and client:
$socket = stream_socket_client(’tcp://0.0.0.0:1037’);
stream_filter_append($socket, ’zlib.inflate’);
while (!feof($socket)) {
echo fread($socket, 100);
}
fclose($socket);
If you consider how complex the implementation of a similar compression mechanism
would have normally been, it’s clear that stream filters are a very powerful
feature.
Licensed to 482634 - Amber Barrow (itsadmin@deakin.edu.au)
Summary
As you can see, streams penetrate to the deepest levels of PHP, from general file access
to TCP and UDP sockets. It is even possible to create your own stream protocols
and filters, making this the ultimate interface for sending and receiving data with