我有以下php代码
$thread_pick=mysqli_query($db,'SELECT * FROM u_mess WHERE participant_1="'.$display_name.'" OR participant_2="'.$display_name.'" ') or trigger_error(mysqli_error());
if(mysqli_num_rows($thread_pick) >= 1 )
{
while($row = mysqli_fetch_assoc($thread_pick))
{
$thread_pick_sub = mysqli_query($db,'SELECT * FROM u_mess_thread WHERE (thread_id="'.$row['thread_id'].'" AND mess_to="'.$display_name.'" )')or trigger_error(mysqli_error());
echo mysqli_num_rows($thread_pick_sub).'dsddsds';
$mess_num_count = mysqli_num_rows($thread_pick_sub);
}
}
我的问题是：该表有两个用户，用户1发送了3条消息，用户2发送了2条消息，现在变量$mess_num_count内的期望值应该是5，但它显示了2我该怎么做才能使其工作
我认为它只计算来自user 2的消息，所以它是2！
要获得5，您必须使用操作员+=，如下所示：
$mess_num_count += mysqli_num_rows($thread_pick_sub);
代码应该是这样的：
$thread_pick=mysqli_query($db,'SELECT * FROM u_mess WHERE participant_1="'.$display_name.'" OR participant_2="'.$display_name.'" ') or trigger_error(mysqli_error());
$mess_num_count = 0;
if(mysqli_num_rows($thread_pick) >= 1 )
{
while($row = mysqli_fetch_assoc($thread_pick))
{
$thread_pick_sub = mysqli_query($db,'SELECT * FROM u_mess_thread WHERE (thread_id="'.$row['thread_id'].'" AND mess_to="'.$display_name.'" )')or trigger_error(mysqli_error());
echo mysqli_num_rows($thread_pick_sub).'dsddsds';
$mess_num_count += mysqli_num_rows($thread_pick_sub);
}
}