MYSQL: Saving various instances of players - php

Question

I host multiple servers for multiplayer games and I am requiring some help with creating a PHP MySQL script.
I have made scripts for the game servers that output a few variables to a php script. These variables include the player name, a GUID number (Game User ID) and a couple other unimportant things. These are sent to the php script every time a player joins the server.
Anyway what I basically need it to do is every time a player joins the server it saves the player name, guid and join date/timestamp to a row in a MySQL table. The player will always have only one GUID code, which is sort of like their cd-key. What I have at this current time:
if ( $action == "save")
{
$name = mysql_real_escape_string($_GET['name']);
$guid = mysql_real_escape_string($_GET['guid']);
}
mysql_query("INSERT INTO `players` (`name`, `guid`) VALUES ('$name', '$guid') ON DUPLICATE KEY UPDATE `last_joined`=CURRENT_TIMESTAMP")or die(mysql_error());
echo "-10";
die();
Now, this works great as it is. But what I need it to do is; if the player comes on the server with a different name, it will log that instance into a new row and if they come on again with the same name it will update the same row with the current time stamp. And for instance, if they change their name back to the first name they use it will update the row that has that name recorded with the current time stamp.
The only thing I have tried is making the 'name' column, a primary key and on a duplicate entry it would update it. However if I did that and another player came on the server with the same name it would just update the last player's data.
So it needs to record every username a player uses.
There's probably quite a simple solution but I've never had the time to learn to MySQL and I need this done soon.
Thanks for any help.

Answer 1

Make the GUID the primary unique key.
Then instead of just inserting the row, check if that guid exists in the database first and then if it does, update the row. If it doesn't then you can insert it.

Answer 2

You can take a shot for this:
$guid = mysqli_real_escape_string($conn, $_GET["guid"]);
$name = mysqli_real_escape_string($conn, $_GET["name"]);
if (!empty($guid) && !empty($name)) {
//Check if the user exists
$sql = "SELECT COUNT(*) AS cnt FROM players WHERE guid = " . $guid;
$res = mysqli_query($conn, $sql);
$row = mysqli_fetch_assoc($res);
if ($row['cnt']) {
//If yes, update
$sql = "UPDATE players SET `last_joined` = NOW()
WHERE `guid` = " . $guid;
} else {
//If no, insert
$sql = "INSERT INTO players (`guid`, `name`, `last_joined`)
VALUES (" . $guid . ", '" . $name . "', NOW())";
}
mysqli_query($conn, $sql);
echo "-10";
die();
} else {
echo 'Missing parameter';
die();
}
NOTE:
I am using mysqli fucntions, because mysql functions are deprecated. You can use PDO also.