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- <?php
- namespace Drupal\Component\Utility;
- /**
- * Provides user agent related utility functions.
- *
- * @ingroup utility
- */
- class UserAgent {
- /**
- * Identifies user agent language from the Accept-language HTTP header.
- *
- * The algorithm works as follows:
- * - map user agent language codes to available language codes.
- * - order all user agent language codes by qvalue from high to low.
- * - add generic user agent language codes if they aren't already specified
- * but with a slightly lower qvalue.
- * - find the most specific available language code with the highest qvalue.
- * - if 2 or more languages are having the same qvalue, respect the order of
- * them inside the $languages array.
- *
- * We perform user agent accept-language parsing only if page cache is
- * disabled, otherwise we would cache a user-specific preference.
- *
- * @param string $http_accept_language
- * The value of the "Accept-Language" HTTP header.
- * @param array $langcodes
- * An array of available language codes to pick from.
- * @param array $mappings
- * (optional) Custom mappings to support user agents that are sending non
- * standard language codes. No mapping is assumed by default.
- *
- * @return string
- * The selected language code or FALSE if no valid language can be
- * identified.
- */
- public static function getBestMatchingLangcode($http_accept_language, $langcodes, $mappings = []) {
- // The Accept-Language header contains information about the language
- // preferences configured in the user's user agent / operating system.
- // RFC 2616 (section 14.4) defines the Accept-Language header as follows:
- // Accept-Language = "Accept-Language" ":"
- // 1#( language-range [ ";" "q" "=" qvalue ] )
- // language-range = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
- // Samples: "hu, en-us;q=0.66, en;q=0.33", "hu,en-us;q=0.5"
- $ua_langcodes = [];
- if (preg_match_all('@(?<=[, ]|^)([a-zA-Z-]+|\*)(?:;q=([0-9.]+))?(?:$|\s*,\s*)@', trim($http_accept_language), $matches, PREG_SET_ORDER)) {
- foreach ($matches as $match) {
- if ($mappings) {
- $langcode = strtolower($match[1]);
- foreach ($mappings as $ua_langcode => $standard_langcode) {
- if ($langcode == $ua_langcode) {
- $match[1] = $standard_langcode;
- }
- }
- }
- // We can safely use strtolower() here, tags are ASCII.
- // RFC2616 mandates that the decimal part is no more than three digits,
- // so we multiply the qvalue by 1000 to avoid floating point
- // comparisons.
- $langcode = strtolower($match[1]);
- $qvalue = isset($match[2]) ? (float) $match[2] : 1;
- // Take the highest qvalue for this langcode. Although the request
- // supposedly contains unique langcodes, our mapping possibly resolves
- // to the same langcode for different qvalues. Keep the highest.
- $ua_langcodes[$langcode] = max(
- (int) ($qvalue * 1000),
- (isset($ua_langcodes[$langcode]) ? $ua_langcodes[$langcode] : 0)
- );
- }
- }
- // We should take pristine values from the HTTP headers, but Internet
- // Explorer from version 7 sends only specific language tags (eg. fr-CA)
- // without the corresponding generic tag (fr) unless explicitly configured.
- // In that case, we assume that the lowest value of the specific tags is the
- // value of the generic language to be as close to the HTTP 1.1 spec as
- // possible.
- // See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4 and
- // http://blogs.msdn.com/b/ie/archive/2006/10/17/accept-language-header-for-internet-explorer-7.aspx
- asort($ua_langcodes);
- foreach ($ua_langcodes as $langcode => $qvalue) {
- // For Chinese languages the generic tag is either zh-hans or zh-hant, so
- // we need to handle this separately, we can not split $langcode on the
- // first occurrence of '-' otherwise we get a non-existing language zh.
- // All other languages use a langcode without a '-', so we can safely
- // split on the first occurrence of it.
- if (strlen($langcode) > 7 && (substr($langcode, 0, 7) == 'zh-hant' || substr($langcode, 0, 7) == 'zh-hans')) {
- $generic_tag = substr($langcode, 0, 7);
- }
- else {
- $generic_tag = strtok($langcode, '-');
- }
- if (!empty($generic_tag) && !isset($ua_langcodes[$generic_tag])) {
- // Add the generic langcode, but make sure it has a lower qvalue as the
- // more specific one, so the more specific one gets selected if it's
- // defined by both the user agent and us.
- $ua_langcodes[$generic_tag] = $qvalue - 0.1;
- }
- }
- // Find the added language with the greatest qvalue, following the rules
- // of RFC 2616 (section 14.4). If several languages have the same qvalue,
- // prefer the one with the greatest weight.
- $best_match_langcode = FALSE;
- $max_qvalue = 0;
- foreach ($langcodes as $langcode_case_sensitive) {
- // Language tags are case insensitive (RFC2616, sec 3.10).
- $langcode = strtolower($langcode_case_sensitive);
- // If nothing matches below, the default qvalue is the one of the wildcard
- // language, if set, or is 0 (which will never match).
- $qvalue = isset($ua_langcodes['*']) ? $ua_langcodes['*'] : 0;
- // Find the longest possible prefix of the user agent supplied language
- // ('the language-range') that matches this site language ('the language
- // tag').
- $prefix = $langcode;
- do {
- if (isset($ua_langcodes[$prefix])) {
- $qvalue = $ua_langcodes[$prefix];
- break;
- }
- } while ($prefix = substr($prefix, 0, strrpos($prefix, '-')));
- // Find the best match.
- if ($qvalue > $max_qvalue) {
- $best_match_langcode = $langcode_case_sensitive;
- $max_qvalue = $qvalue;
- }
- }
- return $best_match_langcode;
- }
- }
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