Grouping and displaying MySQL results by categories using multidimensional array

Question

I have the following script which creates a multidimensional array from a MySQL query and prints the results according to categories like:

CSF (infection)
Glucose
Protein (Spot Urine)

Blood gases
Bicarbonate (Fluid)
pH (Fluid)
Oxygen partial pressure (tension)(pO2)

Creatinine clearance
Creatinine (Fluid)
Creatinine (24 hour Urine)

$test_groups = array();

$query = "SELECT * FROM 
lab_test, 
model_lab_test_lookup, 
lab_test_group 
WHERE 
lab_test.lab_test_pk = model_lab_test_lookup.lab_test_fk
 AND 
model_lab_test_lookup.lab_test_group_fk = lab_test_group.lab_test_group_pk
 AND 
model_lab_test_lookup.pathway_fk = '$pathway' 
GROUP BY lab_test.lab_test_pk";

$result = mysql_query($query, $connection) or die(mysql_error());

while ($row = mysql_fetch_assoc($result)){

$test_groups[$row['group_name']][] = $row['lab_test'];

}

foreach($test_groups as $group_name => $tests){
        echo '<strong>' . $group_name . '</strong><br />';
        foreach($tests as $test){
               echo $test . '<br />';
        }
        echo '<p>';
    }

Now I want to add columns in addition to $row['lab_test'] (the test name), eg $row['lab_test_pk'] and $row['interval'] and be able to access those columns as happens in the foreach loops.

Like

$test_groups[$row['group_name']] = array(
                    'test_pk' => $row['lab_test_pk'],
                    'test_name' => $row['lab_test'],
                    'interval'  => $row['interval']
                    );

What is the right way of doing this and then accessing the added columns in the last foreach loop?

Answer 1

$row['lab_test_pk'].','.$row['lab_test'].','.$row['interval'];

Try the above line and use . to append.

Answer 2

Using part solution provided by @NMN I have the following working:

while ($row = mysql_fetch_assoc($result)){

    $test_groups[$row['group_name']][] = $row['lab_test_pk'].','.$row['lab_test'].','.$row['interval'];

  }

  foreach($test_groups as $group_name => $tests){
    echo '<strong>' . $group_name . '</strong><br />';
    foreach($tests as $test){
        list($test_pk, $test_name, $test_interval) = explode(',', $test);
        echo $test_pk . '<br />';
        echo $test_name . '<br />';
        echo $test_interval . '<br />';
    }
    echo '<p>';
}