Fixed up a bit of grammar and added a note about backrefs and backslashes.

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@42344 c90b9560-bf6c-de11-be94-00142212c4b1

functions/pcre.xml

@@ -259,9 +259,10 @@ preg_match_all ("/\(?  (\d{3})?  \)?  (?(1)  [\-\s] ) \d{3}-\d{4}/x",
      <example>
       <title>Find matching HTML tags (greedy)</title>
       <programlisting role="php">
-// the \\2 is an example of backreferencing. This tells pcre that
-// it must match the 2nd set of parenthesis in the regular expression
-// itself, which would be the ([\w]+) in this case.
+// The \\2 is an example of backreferencing. This tells pcre that
+// it must match the second set of parentheses in the regular expression
+// itself, which would be the ([\w]+) in this case. The extra backslash is 
+// required because the string is in double quotes.
 $html = "&lt;b&gt;bold text&lt;/b&gt;&lt;a href=howdy.html&gt;click me&lt;/a&gt;
 
 preg_match_all ("/(&lt;([\w]+)[^&gt;]*&gt;)(.*)(&lt;\/\\2&gt;)/", $html, $matches);