expmail/helpers.php

<?php

function getFilename($url){
    $content = get_headers($url,1);
    $content = array_change_key_case($content, CASE_LOWER);

    if ($content['content-disposition']) {
        $tmp_name = explode('=', $content['content-disposition']);
        if ($tmp_name[1]) $realfilename = trim($tmp_name[1],'";\'');
    } else  {
        $stripped_url = preg_replace('/\\?.*/', '', $url);
        $stripped_url = preg_replace('/\\/$/', '', $stripped_url);
        $realfilename = basename($stripped_url);
    } 

    return $realfilename;
}

function checkURL($url) {
    $url = filter_var($url, FILTER_SANITIZE_URL);
    if (filter_var($url, FILTER_VALIDATE_URL) === FALSE || !in_array(strtolower(parse_url($url, PHP_URL_SCHEME)), ['http','https'], true)) return false;
    $file_headers = @get_headers($url);
    if ($httpStatus<400) return true;
    return false;
}