<?php
$file = file_get_contents("public/css/app.css");

preg_match_all("/\.[0-9A-Za-z\-_]+/", $file, $out);

usort($out[0], function ($a, $b) {
    return strlen($b) <=> strlen($a);
});
$arr = array_count_values($out[0]);
print_r($arr);

foreach ($arr as $key => $value) {
    file_put_contents("out.csv", $key . ";" . $value . ";" . strlen($key) * $value ."\r\n", FILE_APPEND);
}