$html_regex = '{
   ^(

      (?: <(\w++) [^>]*+ (?<!/)> (?1) </\2>  # matched pair of tags
        | [^<>]++                            # non-tag stuff
        | <\w[^>]*+/>                        # self-closing tag
        | <!--.*?-->                         # comment
        | <script\b[^>]*>.*?</script>        # script block

      )*+

   )$

}isx';

if (preg_match($html_regex, $html_string))
     echo "block structure seems valid\n";
else
     echo "block structure seems invalid\n";




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Copyright 1997-2024 Jeffrey Friedl