Look at this example. There is a line:
$client =& new xmlrpc_client(\'/xml-rpc\', \'api.quicktate.com\', 80);
$client->return_type = \'xmlrpcvals
Starting with the last question first;
what is the -> in $client->return_type mean?
-> is the operator you use to access properties and methods of an object in PHP. Most languages, such as Java or Javascript use the dot operator for the same thing. It (probably) derives from the C syntax for accessing members of a struct.
Then that first question...
what is the =& ?
The short version is, in your example, it's a relic you no longer need; a hangover from PHP4 which you no longer need if you use PHP5. But note this is specific to your example.
For the long version, so you really understand what's going on read http://derickrethans.nl/talks/phparch-php-variables-article.pdf about References in PHP