A small function to get client-sent HTTP Accept-Language header in PHP

getUserAcceptedLanguages.php

<?php
/*
 * A small function to get client-sent HTTP Accept-Language header.
 *
 * Copyright (C) 2018 Víctor Román Archidona
 * https://www.victorroman.es/
 *
 * Input:
 *  (int, optional): An HTTP Accept-Language header or null if it
 *                   should be taken from $_SERVER environment.
 *
 *  (bool, optional): Return languages sorted by preference.
 *
 * Demo:
 *   <?php
 *   $data = "es-es,es;q=0.8,en-us,en-en;q=0.5,en;q=0.3";
 *   print_r(
 *      getUserAcceptedLanguages($data)
 *   );
 *   ?>
 *
 * Output:
 *   Array
 *   (
 *       [0.8] => es-es,es
 *       [0.5] => en-us,en-en
 *       [0.3] => en
 *   )
 *
 * License:
 *   Unlicense: http://unlicense.org
 */
function getUserAcceptedLanguages($languages = null, $sorted = true)
{
    if ($languages == null)
        $languages = $_SERVER["HTTP_ACCEPT_LANGUAGE"];

    $lang_array = array();
    $lang_len = strlen($languages);
    $lang_pos = 0;

    while ($lang_pos < $lang_len) {
        $buffer_languages = null;
        $buffer_priority  = null;

        /* Get each language block, separated by ';' */
        while ($languages[$lang_pos] != ";" && $lang_pos < $lang_len) {
            $buffer_languages .= $languages[$lang_pos];
            $lang_pos++;
        }

        /* Skips ;q= */
        $lang_pos += 3;

        /* Now we take the priority: */
        while ($languages[$lang_pos] != ","  && $lang_pos < $lang_len) {
            $buffer_priority .= $languages[$lang_pos];
            $lang_pos++;
        }

        $lang_array[$buffer_priority] = $buffer_languages;
        $lang_pos++;
    }

    if ($sorted === true)
        ksort($lang_array, SORT_REGULAR);

    return $lang_array;
}