How to get file extension in PHP_PHP Tutorial

How to obtain the file extension in PHP

At work, we often encounter the need to obtain the file extension. Here I will summarize the following methods for you. (Criticisms and corrections welcome)

Method 1

Function getFileExtend_1($fileName){

$retval="";

$pt=strtpos($fileName,".");

　if($pt){

$retval=substr($fileName,$pt+1,strlen($fileName)-$pt);

　}

　if($retval!==""){

return $retval;

　}

return false;

　}

　?>

Method 2

Function getFileExtend_2($fileName){

　$extend = pathinfo($fileName);

　$extend = strtolower($extend['extension']);

　if(is_string($extend)){

return $extend;

　}

return false;

　}

　?>

Method 3

Function getFileExtend_3($fileName){

　$extend =explode(".",$fileName);

　$va=count($extend)-1;

　$extend =$extend[$va];

　if(is_string($extend)){

return $extend;

　}

return false;

　}

　?>