PHP mysql_connect (localhost / 127.0.0.1) on windows platform
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I am using win 7, apache 2, php 5, mysql 5, all are on the same machine.
I have found an interesting issue, I have the following code:

        $sql = "select * from user1";
		$conn = mysql_connect("localhost", "root", "xxxxxxxx");
		mysql_select_db("test1");
		mysql_query("set names utf8");
		$result = mysql_query($sql, $conn);
		while ($row = mysql_fetch_assoc($result)){
			foreach ($row as $key => $value){
				echo $key." => ".$value." || ";
			}
			echo "<br/>";
		}
		mysql_free_result($result);
		mysql_close($conn);

The running for the above code is over 1 s.

When mysql_connect("127.0.0.1", "root", "xxxxxxxx"), the running time is around 10 ms.

I try to find the underlying reason on the internet, and this is the result:

>I recently moved my development from XP to Windows 7 and found that webpages I had developed were taking 5 seconds long to load. This was unacceptable of course so I had to track down the problem.
I eventually tracked down the offending function/method pdo::construct. I also found that mysql_connect was taking about 1 second to make a connection. After a little googling I found an explaination that php had issues with IPv6 and that you could fix the problem by either disabling IPv6 or switching to the ipaddress 127.0.0.1 when making your connection.

I wonder what the issue of IPv6 on PHP is, just want to get a deeper understaning. Thanks.