PHP面试题之文件目录操作

/**
* 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";