php 获取文件扩展名的三个方法

//取得文件的扩展名
//by bbs.it-home.org
//方法1
function get_ext_file_1($file_name)
{
$retval = "";
$pt = strrpos($file_name, ".");
if ($pt) $retval=substr($file_name, $pt+1, strlen($file_name) - $pt);
return ($retval);
}
//方法2
function get_ext_file_2($file_name)
{
$get_ext_file = pathinfo($file_name);
$get_ext_file = strtolower($get_ext_file["extension"]);
return $get_ext_file;
}
//方法3
function get_ext_file_3($file_name)
{
$get_ext_file =explode("." , $file_name);
$va=count($get_ext_file)-1;
return $get_ext_file[$va];
}
?>