<?php
function extension1() {
	$pathinfo = pathinfo("http://w...content-available-to-author-only...k.com/test.php?somevar"); 
	$query = $pathinfo["extension"];
	if (strpos($query,"?") !== false) 
		return substr($query,0,strpos($query,"?")); 
	return $query;
}
function extension2() {
	$strs = explode(".", 'http://w...content-available-to-author-only...k.com/test.php?somevar');
	$extension = array_pop($strs);
	$pos = strpos($extension,"?");
	if ($pos)
		$extension = substr($extension,0,$pos);
	return $extension;
}

function extension3() {
	$baseName = basename('http://w...content-available-to-author-only...k.com/test.php?somevar');
	$dotPosition = strpos($baseName,".");
	$extension = substr($baseName, $dotPosition+1, strpos($baseName, "?")-$dotPosition-1);
	return $extension;
}

function extension4() {
	$strs = 'http://w...content-available-to-author-only...k.com/test.php?somevar';
	preg_match("/\.(php)(?=\?)/", $strs ,$mathes);
	return $mathes[1];
}

function extension5() {
	$path = parse_url('http://w...content-available-to-author-only...k.com/test.php?somevar');
	$extension = substr($path["path"], strpos($path["path"], '.')+1);
	return $extension;
}

var_dump(extension1());
var_dump(extension2());
var_dump(extension3());
var_dump(extension4());
var_dump(extension5());