SQL
If you want a count, ask for a count. Don't ask the server to send all the data for all the rows, just to have the client count the rows. (A few hundred rows is a trivial amount of data for a database to handle, but still, you should follow good practices.)
SELECT SUM(*inactive_count) AS obj_countinactive_count
FROM (
SELECT COUNT(article_active) AS inactive_count
FROM wcx_articles WHERE article_active = '0'
UNION ALL
SELECT COUNT(video_active)
FROM wcx_videos WHERE video_active = '0'
UNION ALL
SELECT COUNT(app_active)
FROM wcx_apps WHERE app_active = '0'
UNION ALL
SELECT COUNT(link_active)
FROM wcx_links WHERE link_active = '0'
) AS wcs_objects;
Schema
If in fact all four of your tables are union-compatible with each other, then you should strongly consider merging them into one table with a wcx_type attribute that declares what type of object that row represents.
Are your …_active columns really strings? Those columns should be of the BOOLEAN (i.e., TINYINT(1)) type. The query should be adjusted accordingly: use …_active = 0 instead of …_active = '0'.
PHP
You reused the $query parameter to store the result of the query. Don't be stingy like that — it's confusing. Use a new variable to store the result.
You have a leak: mysqli_free_result( $query ); never gets called, because that statement is unreachable.
You are mixing the object-oriented and procedural styles of mysqli. You should either use the object-oriented style consistently…
public function num_rows($query) {
if (!($result = $this->link->query($query))) {
$this->log_db_errors($this->link->error, $result, 'Fatal');
return $this->link->error;
}
$num_rows = $result->num_rows;
$result->free();
return $num_rows;
}
or use the procedural style consistently…
public function num_rows($query) {
if (!($result = mysqli_query($this->link, $query))) {
$this->log_db_errors(mysqli_error($this->link), $result, 'Fatal');
return mysqli_error($this->link);
}
$num_rows = mysqli_num_rows($result);
mysqli_free_result($result);
return $num_rows;
}
