Count total posts related to a forum - PHP Logic

Question

I need some help with figuring out the logic for this, because in the most tutorials i saw, they just had to store a topics_count int in the database and every time a topic was created in that specific forum they would increase the topics_count +1 for the forum they were created in;

however can't we achieve this by getting a value using mysqli_num_rows instead? This would return the total rows (topics) in relation with a forum. But then the problem is how can i create that relation when the forums are inside an array.

Both forums and topics have an:

• id
• title
• description

I am aware of the security problems. This example is just a practice.

This is how i display the forums from the database and echo a href to each forum.

                $array_forums = mysqli_fetch_assoc($res_forums); 
                    echo "<div id='forum_{$array_forums["forum_id"]}' class='forum_classic'>";
                        echo "<div id='forum_classic_status'></div>";                           
                        echo "<div id='forum_classic_container'>";
                            echo "<div id='forum_classic_icon'></div>";
                            echo "<div id='forum_classic_description'>";
                                    echo "<a href=forum.php?forum=" . urlencode($array_forums["forum_id"]) . ">";
                                        echo "<h1>{$array_forums["forum_title"]}</h1>";
                                    echo "</a>";
                                echo "<p>{$array_forums["forum_description"]}</p>";
                            echo "</div>";
                        echo "</div>";
                        echo "<div id='forum_classic_topics'>Topics</div>";
                        echo "<div id='forum_classic_replies'>Replies</div>";
                        echo "<div id='forum_classic_lastposter'>Lastposter</div>";
                    echo "</div>";
                }

This is how i display the topics in each forum, after a link is clicked.

            $forum_id = $_GET['forum'];

            //1. Perform database query for topics
            $sql_topic = "SELECT * FROM topics WHERE topic_forum_id = {$forum_id}";
            $res_topic = mysqli_query($conn, $sql_topic);
            //2. Display returned data from topics
            if (mysqli_num_rows($res_topic) >= 1) {
                $array_topic = mysqli_fetch_assoc($res_topic);
                echo "<div id='topic_{$array_topic["topic_id"]}'>{$array_topic["topic_title"]}";
                echo "</div>";
            } else {
                echo "<a href='community.php'>Return To Forum Index</a>";
                echo "<p>There are no topics in this forum yet.</p>";
            }

Answer 1

With the help of @Anil Shrestha , $num will serve as the topic counter.

                    $sql_topic = "SELECT count(*) FROM topics WHERE topic_forum_id = {$array_forums["forum_id"]}";
                    $res_topic = mysqli_query($conn, $sql_topic);
                    $row = mysqli_fetch_row($res_topic);
                    $num = $row[0];

Answer 2

You can use count to count the number of rows

$sql_topic = "SELECT count(*) FROM topics WHERE topic_forum_id = {$forum_id}";
$row = mysqli_fetch_row($sql_topic);
$num = $row[0];

$num will return the number of topics in specific forum