php gets the file extension in url

//Get the file extension in the url address
$url = "http://sdk.tools.sinaapp.com/index.php?appname=beipiao&version=1";
function getFileName($url){
 $a = explode('?', $url);
$b = strrpos($a[0], '.'); //strrpos (searched string, to find string, [search starting position] ) Find the position of the last occurrence of the string: if found, return the position of the last occurrence; if not found, return false
$c = substr($a[0], $b+1, 3); //substr(operated String, start position, [end position]) Return part of the string
return $c;
}
echo getFileName($url)."";
//Second method
function getFileNameTwo($ url){
$a = parse_url($url, PHP_URL_PATH); //parse_url() parses the url and returns its components
$b = pathinfo($a, PATHINFO_EXTENSION); //pathinfo()
return $b;
 }
print_r(getFileNameTwo($url));

file extension, php, url