Using http_get

Yahoo has an api that lets you do geocoding that uses http_get. When I went to run http_get, I get an error

Fatal error: Call to undefined function http_get() in

I don’t see an http_get.dll in php.ini or an actual dll file in the ext subdirectory. And I can’t find much constructive advice anywhere else. Anyone know if this the http_get function can be used in php and if not, how can I call an external api from within php. Thanks

This is what you are looking for: http://us.php.net/manual/en/book.http.php
What version of PHP and what server are you using on what OS?