/**
* 5种方式获取文件后缀名
* 这道题其实就是考函数substr() strrchr()  array_pop()  strrpos() strpos() strrev() explode()  pathinfo()
* @param string $filename 要处理的文件名  1.jpg/1.png/1.html/1.php
* @return string .php/php  
*/
function get_ext1($filename)
{
        return strrchr($filename,'.');
}

function get_ext2($filename){
        return substr($filename,strrpos($filename,'.'));
}

function get_ext3($filename){
        return array_pop(explode('.',$filename));
}

function get_ext4($filename){
        return pathinfo($filename,PATHINFO_EXTENSION);
}

function get_ext5($filename){
        return strrev(substr(strrev($filename),0,strpos(strrev($filename),'.')));
}

$filename = "1.php";
echo get_ext1($filename)."\n";
echo get_ext2($filename)."\n";
echo get_ext3($filename)."\n";
echo get_ext4($filename)."\n";
echo get_ext5($filename)."\n";

/**
* 遍历目录(递归)
* @param string $dir 目录名且最后没有/
* @return array $files 整个目录结构
*/
function myScandir($dir)
{
        $files = array();
        if($handle = opendir($dir)){
                while (($file = readdir($handle)) != false){
                        if($file != "." && $file != ".."){
                                $newDir = $dir."/".$file;
                                if(is_dir($newDir)){
                                        $files[$file] = myScandir($newDir);
                                }else{
                                        $files[] = $file;
                                }
                        }
                }
                closedir($handle);
                return $files;
        }
}

$dir = "/dirname";
print_r(myScandir($dir));