改变计划，因为我误解了设置。
您将希望一次性从每个“类型”表中提取所有数据，而不是基于每个通知。这意味着您将需要循环两次通知，一次获取所有 id 和适当的类型，然后第二次输出结果。
function showNotifications($userid){
$STH = $this->database->prepare('SELECT * FROM notifications WHERE user_id = :userid ORDER BY timestamp DESC');
$STH->execute(array(':userid' => $userid));
// Centralized Book keeping for the types.
// When you add a new type to the entire system, add it here as well.
$types = array();
// Add the first notification type
$types["1"] = array();
// "query" is pulling all the data you need concerning a notification
$types["1"]["query"] = "SELECT m.id, u.username, u.firstname FROM messages m, users u WHERE m.sender = u.id AND m.id IN ";
// "ids" will hold the relevant ids that you need to look up.
$types["1"]["ids"] = array();
// A second type, just for show.
// $types["2"] = array();
// $types["2"]["query"] = "SELECT a.id, u.username, u.firstname FROM articles a, users u WHERE a.sender = u.id AND a.id IN ";
// $types["2"]["ids"] = array();
// Use fetchAll to gather all of the notifications into an array
$notifications = $STH->fetchAll();
// Walk through the notifications array, placing the notification id into the corret
// "ids" array in the $types array.
for($i=0; $i< count($notifications); $i++){
$types[$notifications[$i]['type']]["ids"][] = $notifications[$i]['feature_id'];
}
// Walk through the types array, hit the database once for each type of notification that has ids.
foreach($types as $type_id => $type){
if(count($type["ids"]) > 0){
$STH = $this->database->prepare($type["query"] . "( " . implode(",", $type["ids"]) . " )");
$STH->execute();
// Creates a hash table with the primary key as the array key
$types[$type_id]['details'] = $STH->fetchAll(PDO::FETCH_GROUP|PDO::FETCH_ASSOC);
$types[$type_id]['details'] = array_map('reset', $types[$type_id]['details']);
// run array_map to make it easier to work with, otherwise it looks like this:
// $results = array(
// 1234 => array(0 => array('username' => 'abc', 'firstname' => '[...]')),
// 1235 => array(0 => array('username' => 'def', 'firstname' => '[...]')),
// );
}
}
// Now walk through notifications again and write out based on notification type,
// referencing $types[<notification type>]["details"][<message id>] for the details
for($i=0; $i< count($notifications); $i++){
// check to see if details for the specific notification exist.
if(isset($types[$notifications[$i]['type']]["details"][$notifications[$i]['feature_id']])){
$notification_details = $types[$notifications[$i]['type']]["details"][$notifications[$i]['feature_id']];
switch ($notifications[$i]['type']) {
case "1":
echo '<li><i>'.timeAgo($notifications[$i]['timestamp']).'</i><a href="user.php?username=' . $notification_details['username'] . '">' . $notification_details['first_name'].'</a> sent you a <a href="inbox.php?message='.$notifications[$i]['feature_id'].'">message</a></li>';
break;
}
}
}
}
更新：添加了逻辑以在未提取任何详细信息时跳过通知（例如，消息或用户已被删除）
我认为您想运行一个查询，该查询通过连接或更复杂的 where 语句收集所有信息。
选项 1：这可能需要调整，以免表格的笛卡尔积
SELECT n.id, n.type, m.id, m.body, u.username, u.first_name
FROM notifications n, messages m, users u
WHERE n.user_id = :userid AND m.id = n.feature_id AND u.id = m.sender
选项 2：如果表别名不起作用，那么您需要用完整的表名替换它们
SELECT SELECT n.id, n.type, m.id, m.body, u.username, u.first_name
FROM notifications n
JOIN messages m
ON n.feature_id = m.id
JOIN users u
ON m.sender = u.id
WHERE n.user_id = :userid