Пример работы:
<?php
$fileext=extension("file.exe"; // $fileext равно exe
$fileext=extension("FILE.sub.ExE"; // $fileext равно exe
?>

                        
<?php

function pathinfo_utf($path, $options="") {  

    if(strpos($path, '/') !== false){ 

        $basename = end(explode('/', $path)); 

    }elseif(strpos($path, '\') !== false){ 

        $basename = end(explode('\', $path)); 

    }else{ 

        return(false); 

    } 

    if(empty($basename))    { 

        return(false); 

    } 



    $dirname = substr($path, 0, strlen($path) - strlen($basename) - 1);



    if (strpos($basename, '.') !== false) 

    { 

        $extension = end(explode('.', $path)); 

        $filename = substr($basename, 0, strlen($basename) - strlen($extension) - 1);

    } 

    else 

    { 

        $extension = ''; 

        $filename = $basename; 

    } 

     

    switch($options){ 

        case PATHINFO_DIRNAME: 

            return($dirname); 

        break; 

        case PATHINFO_BASENAME: 

            return($basename); 

        break; 

        case PATHINFO_EXTENSION: 

            return($extension); 

        break; 

        case PATHINFO_FILENAME: 

            return($filename); 

        break; 

        default: 

            return( 

                array( 

                    'dirname' => $dirname, 

                    'basename' => $basename, 

                    'extension' => $extension, 

                    'filename' => $filename 

            )); 

        break; 

    } 

} 



function extension($file){ 

    if(function_exists('pathinfo_utf')){ 

        $ext = pathinfo_utf($file, PATHINFO_EXTENSION); 

    }else{     

        $ext = pathinfo($file, PATHINFO_EXTENSION); 

    } 

    $ext = strtolower($ext); 

    return($ext); 

} 

?>

?>