+
+ /**
+ * @param DOMDocument $doc
+ * @return string|null Lowercase charset
+ */
+ public static function extractCharset(DOMDocument $doc): ?string
+ {
+ $xpath = new DOMXPath($doc);
+
+ $expression = "string(//meta[@charset]/@charset)";
+ if ($charset = $xpath->evaluate($expression)) {
+ return strtolower($charset);
+ }
+
+ try {
+ // This expression looks for a meta tag with the http-equiv attribute set to "content-type" ignoring case
+ // whose content attribute contains a "charset" string and returns its value
+ $expression = "string(//meta[@http-equiv][translate(@http-equiv, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'content-type'][contains(translate(@content, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'charset')]/@content)";
+ $mediaType = MediaType::fromContentType($xpath->evaluate($expression));
+ if (isset($mediaType->parameters['charset'])) {
+ return strtolower($mediaType->parameters['charset']);
+ }
+ } catch(\InvalidArgumentException $e) {}
+
+ return null;
+ }