Description:
------------
libcurl accepts callback functions for various events, such as a handle receiving data. The documentation says:

"value should be a string that is the name of a valid callback function"

Actually, curl_setopt() also accepts a closure for these options, as shown by the test script supplied in this report.

A closure or anonymous function, not a string containing the name of a function, should in fact be the recommended way to set these options. A string name is (presumably) looked up in the PHP script's global scope and such a function cannot access any state information from the local scope of the caller of curl_setopt(), making that much less useful.

Test script:
---------------
function do_a_curl_thing() {
	$handle = curl_init();
	$some_state_information = "foobar";
	curl_setopt($handle, CURLOPT_URL, "http://www.php.net");
	curl_setopt(
		$handle,
		CURLOPT_WRITEFUNCTION,
		function($res, $data) use ($some_state_information) {
			echo "do something with the data that came in " . $data;
			echo "while possibly consulting or mutating ";
			echo $some_state_information;
		}
	);
	curl_exec($handle);
}

do_a_curl_thing();

Expected result:
----------------
The documentation should state:

value should be a valid callback function, specified either directly as a closure or anonymous function, or as a string that is the name of such a function. Specifying a function directly is recommended.

Actual result:
--------------
The documentation states:

value should be a string that is the name of a valid callback function