Help with Array to string conversion

[mattix]

How can I get rid of  "Notice:Array to string conversion on line 78" error from this code?  can i get a little help please? 

This is line 78 :         $table .= $columnValue;

Basically this code's supposed to do is to group the values from grpa, grpb of datatb to 4 different categories according to their value. and as end result, category index number  of each category is put into the html table.

Thanks.

 

<?php

 include ("configd.php");

  $sql = "SELECT grpa, grpb From datatb";
  $result = $conn->query($sql);
  
  //categories
  
  $cat = [
    4 => [1, 2, 3, 4],
    3 => [5, 6],
    2 => [7, 8],
    1 => [9, 10]
];
while ($row = $result->fetch_assoc()) {
    foreach ($cat as $catKey => $catValue) {
        $columns[$catKey] = array_filter($row, function ($col) use ($cat, $catKey) {
            if (in_array($col, $cat[$catKey])) {
                return true;
            }
        });
    }

    $output[] = $columns;
}


// the output 

$table = <<<EOT
<table class='maintable'>
    <tr><th>9:10</th></tr>
    <tr><th>7:8</th></tr>
    <tr><th>5:6</th></tr>
    <tr><th>1:4</th></tr>
</table>

EOT;


foreach ($output as $row) {
    $table .= "<table class='maintable'>";

    foreach ($row as $columnKey => $columnValue) {
        $table .= "<tr>";
        $table .= "<td>";
        $table .= $columnValue;
        $table .= "</td>";
    }

    $table .= "</tr>";
    $table .= "</table>";
}




echo $table;

?>

 

Edited June 30, 2020 by mattix
small additions.

[gw1500se]

You don't say what data type '$columnValue' is so I am assuming it is int.

$table .= strval($columnValue);

 

[mattix]

true. thanks. but  even though i made the change you proposed, i  still get the same error. 

[Barand]

perhaps

$table .= join(',', $columnValue);

 

[mattix]

yes, this doesn't give error. but it doesn't list the category keys, it lists category values.  any ideas there too? if not, thanks anyway.

[Barand]

$table .= $columnKey 

?

[mattix]

I tried this before, it lists all category keys in the html table. 

It's supposed to list only the category key numbers that matches the value, if not the output to be blank. 

 

Edited June 30, 2020 by mattix

[Barand]

Why don't you reveal the data in the datatb table so we can see the input.

Then show us what the output should look like from that data.

That way we might able to see the path from one to the other.

[mattix]

This is the data on the  table. 

id,  grpa,  grpb
1,  1,  5
2,  4,  6
3,  8,  9
4,  3,  3
5,  5,  4
6,  7,  8
7,  9,  10
8,  10,  5
9,  10,  9

and this the desired table from the original table. 

 

 

 

I showed the expected table in horizontal view to prevent confusion. My real table is vertical in the code. 

 

 

Edited June 30, 2020 by mattix

[Barand]

I created an extra table to define which category the values were in

mysql> select * from catval;
+-----+------+
| val | cat  |
+-----+------+
|   1 |    4 |
|   2 |    4 |
|   3 |    4 |
|   4 |    4 |
|   5 |    3 |
|   6 |    3 |
|   7 |    2 |
|   8 |    2 |
|   9 |    1 |
|  10 |    1 |
+-----+------+

then

    $sql = "SELECT a.cat as cata
               , b.cat as catb 
          FROM datatb d 
               JOIN catval a ON d.grpa = a.val
               JOIN catval b ON d.grpb = b.val
         ";
    $result = $db->query($sql);

    //categories

    $cat = [
            4 => ['name'=>'1:4', 'recs'=>[]],
            3 => ['name'=>'5:6', 'recs'=>[]],
            2 => ['name'=>'7:8', 'recs'=>[]],
            1 => ['name'=>'9:10','recs'=>[]]
         ];
         
    $n = 0;
    while ($row = $result->fetch_assoc()) {
       $cat[$row['cata']]['recs'][$n][] = $row['cata'];
       $cat[$row['catb']]['recs'][$n][] = $row['catb'];
       $n++;
    }

    // the output 
    echo "<table border='1' style='width:500px; border-collapse:collapse;'>";

    foreach ($cat as $c) {
        echo "<tr><th>{$c['name']}</th>";
        for ($i=0; $i<$n; $i++) {
            echo '<td style="text-align:center;">' . (isset($c['recs'][$i]) ? join(',', $c['recs'][$i]) : '&ndash;') . "</td>";
        }
        echo "</tr>\n";
    }
    echo "</table>\n";

[mattix]

Thank you, Barand. This is all new. I'll work on this.