How to implement multi-level associated multi-dimensional arrays in PHP and Mysql?

Question

As shown in the figure, a User has multiple topics, and each topic has a corresponding theme. Please tell me how to achieve this relationship in php+mysql?

给我你的怀抱 · Answer

Do you mean the actual table structure, or how to query this data form

I don’t know if you wrote it in a framework or natively

// 查詢USER表
$returndata = array();
while($userdata = mysql_fetch_assoc()) {
   
    $id = $userdata['id'];
    //跟著根據id查詢topics
    $topicssql = "";
    .....
    $userdata['topics'] = array();
    while($topicsd = mysql_fetch_assoc()) {
        $userdata['topics'][] = $topicsd; 
    }
}

给我你的怀抱 · Answer

This is usually done by merging the retrieved data in the background