获取文件名后缀的方法

function ext1($str){
   // $info = pathinfo($str);
   // return $info['extension'];
   return pathinfo($str, PATHINFO_EXTENSION);
}
echo ext1('test.abc.html');

function ext2($str){
   $arr = explode('.',$str);
   $count = count($arr);
   return $arr[$count-1];
}
echo ext2('test.abc.html');

function ext3($str){
   return trim(strrchr($str,'.'),'.');
}
echo ext3('test.abc.html');

function ext4($str){
   while(strpos($str,'.')){
      $num = strpos($str,'.');
      $str = trim(substr($str,$num),'.');
      // echo $str;exit;
   }
   return $str;
}
echo ext4('test.abc.html');
echo "<hr>";

function ext5($str){
   while(strstr($str,'.')){
      $str = trim(strstr($str,'.'),'.');
      // echo $str;exit;
   }
   return $str;
}
echo ext5('test.abc.html');