Fix for the db error when re-activating

This plugin uses dbDeltas incorrectly. The problem can be seen if you de-activate and then activate the plugin. Due to errors, you will not be able to activate the plugin. (This may require WP_DEBUG.)

In wps-install.php the dbDelta strings should look like this:

$create_useronline_table = ("CREATE TABLE {$wp_prefix}statistics_useronline (
			ID int(11) NOT NULL AUTO_INCREMENT,
			ip varchar(20) NOT NULL,
			timestamp int(10) NOT NULL,
			date datetime NOT NULL,
			referred text CHARACTER SET utf8 NOT NULL,
			agent varchar(255) NOT NULL,
			platform varchar(255),
			version varchar(255),
			PRIMARY KEY  (ID)
		) CHARSET=utf8");

The two fixes are:
#1. Remove all bactick characters.
#2. Put two spaces between “PRIMARY KEY” and “(ID)”

It is unfortunate but true that WP dbDelta cannot handle backticks. The preg_match() in line 1669 (WP 3.9.2) of wp-admin/includes/upgrade.php will fail:
preg_match("|".$tablefield->Field." ([^ ]*( unsigned)?)|i",...
and the following line
$fieldtype = $matches[1];
will emit a warning if you turn on WP_DEBUG.

The failure to match causes WP to try to recreate the table columns. That is usually OK, but not what you want.

Problem #2 is worse, because MySQL will try to add an index that already exists. It is unfortunate but true that you need two spaces in there. MySQL does not see a difference, but WP does, due to the array_search() at line 1745.

The other KEY lines should *not* have the double space, only the PRIMARY KEY. So problem #1 affects 5 strings; problem #2 is in 4 strings.

https://wordpress.org/plugins/wp-statistics/