/**
*
 * 五種方法獲取文件擴展名
 **/
$file_name="aa.txt";
echo strrchr($file_name, ‘.‘);
echo ‘<hr/>‘;
echo substr($file_name, strrpos($file_name, ‘.‘));
echo ‘<hr/>‘;
$arr=explode(‘.‘,$file_name);
echo array_pop($arr);
echo ‘<hr/>‘;
echo pathinfo($file_name)[‘extension‘];
echo ‘<hr/>‘;
echo
 
 strrev(substr(strrev($file_name), 0, strpos(strrev($file_name), ‘.‘)));

php多種方式獲得文件擴展名