text input (seperated by comma) mysql input as array - php

Question

I have a form where I am trying to implement a tag system.
It is just an:
<input type="text"/>
with values separated by commas.
e.g. "John,Mary,Ben,Steven,George"
(The list can be as long as the user wants it to be.)
I want to take that list and insert it into my database as an array (where users can add more tags later if they want). I suppose it doesn't have to be an array, that is just what seems will work best.
So, my question is how to take that list, turn it into an array, echo the array (values separated by commas), add more values later, and make the array searchable for other users. I know this question seems elementary, but no matter how much reading I do, I just can't seem to wrap my brain around how it all works. Once I think I have it figured out, something goes wrong. A simple example would be really appreciated. Thanks!
Here's what I got so far:
$DBCONNECT
$artisttags = $info['artisttags'];
$full_name = $info['full_name'];
$tel = $info['tel'];
$mainint = $info['maininst'];
if(isset($_POST['submit'])) {
$tags = $_POST['tags'];
if($artisttags == NULL) {
$artisttagsarray = array($full_name, $tel, $maininst);
array_push($artisttagsarray,$tags);
mysql_query("UPDATE users SET artisttags='$artisttagsarray' WHERE id='$id'");
print_r($artisttagsarray); //to see if I did it right
die();
} else {
array_push($artisttags,$tags);
mysql_query("UPDATE users SET artisttags='$artisttags' WHERE id='$id'");
echo $tags;
echo " <br/>";
echo $artisttags;
die();
}
}

Answer 1

Create a new table, let's call it "tags":
tags
- userid
- artisttag
Each user may have multiple rows in this table (with one different tag on each row). When querying you use a JOIN operation to combine the two tables. For example:
SELECT username, artisttag
FROM users, tags
WHERE users.userid = tags.userid
AND users.userid = 4711
This will give you all information about the user with id 4711.
Relational database systems are built for this type of work so it will not waste space and performance. In fact, this is the optimal way of doing it if you want to be able to search the tags.