How does the regular match both modes?

How regular matches both modes
I don't know how to articulate what I mean, for example.

PHP Code

  
  $content = "Xxxhttp://xxx.com/hello.htmlxxx";p reg_match_all ("/http:\/\/xxx\.com\/[\w|") {4,17}\.html/ius ", $content, $result);//will get the result array ([0] = = Array (    [0] = http://xxx.com/hello.html    ))

I want to get the expression at the same time to represent the Hello what to do?

------Solution--------------------
The actual operation upstairs has been written

I offer two reference links
Http://deerchao.net/tutorials/regex/regex.htm
This is my reference document for the regular notation.

http://cn.php.net/manual/zh/reference.pcre.pattern.syntax.php
This is a reference manual for the pcre regular used by PHP.
------Solution--------------------
The landlord does not have the regular practice familiar, need to put the meaning of the regular symbols, make clear, then it is not difficult.

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