Of course we want to know how and where this widget is being used so we can decide if it’s worth doing more widgets in the future, so we needed to include tracking. What we want to know is where the widget is being used, and how many times it is being displayed on those URLs.

The tracking table is very simple:

CREATE TABLE widget_impressions
(
	id int(11) NOT NULL auto_increment,
        referral_url varchar(255) NOT NULL,
        counter int(11) NOT NULL,
        date_created date NOT NULL,
        PRIMARY KEY  (referral_url,date_created),
        UNIQUE KEY id (id)
)

Technically, the id column is not needed since the primary key is a combination of the referral_url and the date_viewed field, but it can be handy in some situations.

When the widget is displayed, the following query is run:

INSERT INTO widget_impressions
	SET
		referral_url = 'http://example.com',
		date_viewed = now(),
		counter = 1
	ON DUPLICATE KEY UPDATE
		counter = counter + 1;

If this is the first visit from http://example.com for the day, a new record will be added to the table. If it’s not the first record for the day, the counter will be incremented by one. Using the date type for the date_viewed field means only the date is stored, not the time. If a datetime field were used, this method would not work the same way; we’d have separate entries in the table every time someone viewed the widget.

With this table structure it’s very easy to get stats. Say you want to know all of the pages where the widget is displayed and how many times it has been displayed on each:

SELECT referral_url, SUM(counter) as num_views
FROM widget_impressions
GROUP BY referral_url;

Want to know the 10 sites that are displaying your widget the most?

SELECT referral_url, SUM(counter) as num_views
FROM widget_impressions
GROUP BY referral_url
ORDER BY num_views DESC
LIMIT 10;

References:

• MySQL – on duplicate key update
• Overview of Date and Time Types
• now()

// $id would have been set based on some other operation above.
// I'm setting it here for clarification.
$id = 1;
 
$result = mysql_query("SELECT id FROM table_name WHERE id = $id");
 
if(mysql_num_rows() == 0)
{
     // Zero results, the record doesn't exist, add it.
     mysql_query("INSERT INTO table_name (id,a,b) VALUES ($id,2,3)");
}
else
{
     // The record exists, update it.
     mysql_query("UPDATE table_name SET a = 1, b = 2 WHERE id = $id");
}

Well, thanks to the ON DUPLICATE KEY UPDATE option in MySQL this can be condensed to the following:

$result = mysql_query("INSERT INTO table_name SET id = $id, a = 2, b = 3
					 ON DUPLICATE KEY UPDATE
					 a = 2, c = 3");

Notes:

• You don’t have to update every field on update. If you only need one row updated if the row already exists, specify only that row in the UPDATE portion of the query.
• I prefer the above syntax (using set and writing field = value for each field) but as shown in the MySQL manual, it works with the (field1,field2,field3) VALUES (value1,value2,value3) version as well.
• This method does not work perfectly in all situations! Be sure to test on your dev server before using in production!