如何计算while循环内查询的行数？

Question

i have the following php code

$thread_pick=mysqli_query($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);
  }
}

my problem:the table has two users user 1 has sent 3 messages and user 2 has sent 2 messages now the expected value inside variable $mess_num_count should be 5 but it is showing 2 what do i do to make it work

Answer 1

I think it's only counting the messages from user 2 so it's 2 !

To get 5 you have to use the operator += like this:

$mess_num_count += mysqli_num_rows($thread_pick_sub);

The code should then look like this:

$thread_pick=mysqli_query($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);
  }
}