当没有该单元格的数据时，我想在表格中显示一个空单元格

Our organisation offers morning & afternoon ski tours at several different levels. Not all tour levels occur every session and sometimes there may be more than one tour at a given level at the same time. I want to display guest numbers by date, type of tour and time of day. I have no problem retrieving the numbers, my problem is the display. Where there is no data I can't figure out how to make it show a blank cell, or one with a 0 in it.

The image shows a sample of what I'm getting, which I modified a bit to show what I want.

Hopefully this will clarify my issue. On Mar 28 there were guests for all 5 types of tours in the morning and afternoon. On Mar 29 no one took the BlGrn Tour so its amID value of 2 does not exist in the database for that date (see below), nor does the pmID value of 1 for the Grn tour appear for that afternoon and all the cells with data get shifted to the left.

memberID    amID    pmID    date    guestsAM    guestsPM    statsID
   191        5      5  28/03/2016     2           1    17322
   192        4      3  28/03/2016     4           4    17323
   52         0      1  28/03/2016     0           2    17324
   408        5      4  28/03/2016     2           7    17325
   370        0      2  28/03/2016     0           2    17326
   624        3      3  28/03/2016     3           5    17327
   480        1      2  28/03/2016     3           5    17329
   571        4      0  28/03/2016     3           0    17330
   427        3      0  28/03/2016     2           0    17331
   528        2      0  28/03/2016     3           0    17332

   13         4      2  29/03/2016     3           4    17333
   179        5      0  29/03/2016     3           0    17334
   147        1      0  29/03/2016     3           0    17335
   571        0      4  29/03/2016     0           2    17336
   426        0      3  29/03/2016     0           2    17338
   100        0      3  29/03/2016     0           3    17339
   165        3      0  29/03/2016     5           0    17340
   480        5      0  29/03/2016     1           0    17341
   427        1      5  29/03/2016     2           4    17342
   613        3      0  29/03/2016     4           0    17343

This is the code which retrieves the morning data. If there is more than one tour of a given type at the same time this code successfully adds up the guest numbers for those tours.

$sql = "SELECT *, SUM(guestsAM) as guestsam FROM stats GROUP BY date, amID";
$mar_am_tour = mysqli_query($dbc,$sql) or die(mysqli_error());

This is one variant of the code that I have tried to display the data for one tour type. If amID occurs for that date it works like a charm. If not it simply moves what should be in the next cell into the empty space. (see the image)

while($row = mysqli_fetch_array($mar_am_tour)) {
    if ($row[date] == '2016-03-29') { 
        if ($row[amID] == 1) {
            echo '<td class="members">' . $row[guestsam] .  '</td>'; 
        } else  {
            if ($row[amID] == '') {
                echo '<td class="members"></td>';
            }
        }
    }

I've also tried replacing Srow[amID] with $row[guestsam] == 0 and $row[guestsam] == '' in the 'else' statement and reversing the order of the if statements. Replacing the if statement after the "else" with

echo '<td class="members"></td>';

results in an empty cell between each cell with data.

I think what I need is something along the lines of

if ($row[amID] == 1 does not exist for this date ) { echo '';

I found this

function is_blank($value) {
return empty($value) && !is_numeric($value);

}

on "How to implement is_empty" but I have no idea if it's what I need nor how to use it.

As mentioned by RST, check for value that $row[amID] has when the cell needs to be empty. Also, your code has trivial mistake

while($row = mysqli_fetch_array($mar_am_tour)) {
if ($row['date'] == '2016-03-29') { 
    if ($row['amID'] == 1) {
        echo '<td class="members">' . $row['guestsam'] .  '</td>'; 
    } else  {
        if (!empty($row['amID'])) {
            echo '<td class="members"></td>';
        }
       /*what if $row['amID'] != '' . 
        *Either put an else block here or remove the if block and just 
        *echo '<td class="members"></td>'
        */
    }
}