Escaped hyphens in regex character classes

The hyphens triggered warnings in PHP v7.3.0. Escaping them can be done safely, since it is compatible with other versions of PHP, which were simply a little more tolerant.

A bit more information can be found here: https://stackoverflow.com/questions/26208622/preg-match-compilation-failed-invalid-range-in-character-class-at-offset-15

simple_html_dom.php

@@ -721,7 +721,7 @@ protected function parse_selector($selector_string) {
 // This implies that an html attribute specifier may start with an @ sign that is NOT captured by the expression.
 // farther study is required to determine of this should be documented or removed.
 //        $pattern = "/([\w-:\*]*)(?:\#([\w-]+)|\.([\w-]+))?(?:\[@?(!?[\w-]+)(?:([!*^$]?=)[\"']?(.*?)[\"']?)?\])?([\/, ]+)/is";
-        $pattern = "/([\w-:\*]*)(?:\#([\w-]+)|\.([\w-]+))?(?:\[@?(!?[\w-:]+)(?:([!*^$]?=)[\"']?(.*?)[\"']?)?\])?([\/, ]+)/is";
+        $pattern = "/([\w\-:\*]*)(?:\#([\w\-]+)|\.([\w\-]+))?(?:\[@?(!?[\w\-:]+)(?:([!*^$]?=)[\"']?(.*?)[\"']?)?\])?([\/, ]+)/is";
         preg_match_all($pattern, trim($selector_string).' ', $matches, PREG_SET_ORDER);
         if (is_object($debugObject)) {$debugObject->debugLog(2, "Matches Array: ", $matches);}
 
@@ -927,7 +927,7 @@ function get_display_size()
         {
             // Thanks to user gnarf from stackoverflow for this regular expression.
             $attributes = array();
-            preg_match_all("/([\w-]+)\s*:\s*([^;]+)\s*;?/", $this->attr['style'], $matches, PREG_SET_ORDER);
+            preg_match_all("/([\w\-]+)\s*:\s*([^;]+)\s*;?/", $this->attr['style'], $matches, PREG_SET_ORDER);
             foreach ($matches as $match) {
               $attributes[$match[1]] = $match[2];
             }
@@ -1402,7 +1402,7 @@ protected function read_tag()
             return true;
         }
 
-        if (!preg_match("/^[\w-:]+$/", $tag)) {
+        if (!preg_match("/^[\w\-:]+$/", $tag)) {
             $node->_[HDOM_INFO_TEXT] = '<' . $tag . $this->copy_until('<>');
             if ($this->char==='<') {
                 $this->link_nodes($node, false);