Display several results with one SQL query (group by?) - php

Question

I want to show several results of one query, but I need to group some of these results. I think it's better for you to see my problem :
I have this table that shows several trainings :
And when you click on a row, it'll expand and show exercises that correspond to the training's id (here's example values) :
To get all the exercises by training, I made the following query :
SELECT E.id_entrainement, E.intitule_entrainement, E.date_entrainement, EX.id_exercice, EX.reps, EX.poids, M.nom_exm FROM entrainements E, exercices EX, exercices_muscles M WHERE EX.id_entrainement = E.id_entrainement AND EX.membre = E.id_membre AND M.id_exm = EX.id_exercice_muscle AND id_membre='".$user_id."' GROUP BY E.id_entrainement
But when I put in my code the $data['id_entrainement'] for example, it shows me only the first value got by the query as you can see here :
And when I remove the GROUP BY clause from my query, I have this :
I don't know if it's really helpful for you, but here's my php code :
echo '<div class="container">';
echo '<h1>Vos entraînements</h1>
<table class="table table-striped">
<thead>
<tr>
<th>#</th>
<th>Référence entraînement</th>
<th>Nom de l\'entraînement</th>
<th>Date de réalisation</th>
<th></th>
</tr>
</thead>
<tbody>';
$i=0;
//$getTrainings = $bdd->query("SELECT * FROM entrainements WHERE id_membre='".$user_id."'");
$getTrainings = $bdd->query("SELECT E.id_entrainement, E.intitule_entrainement, E.date_entrainement, EX.id_exercice, EX.reps, EX.poids, M.nom_exm FROM entrainements E, exercices EX, exercices_muscles M WHERE EX.id_entrainement = E.id_entrainement AND EX.membre = E.id_membre AND M.id_exm = EX.id_exercice_muscle AND id_membre='".$user_id."' ");
while ($data = $getTrainings->fetch()) {
$i++;
echo '
<tr class="plusExpand">
<th scope="row">' . $i . '</th>
<td>' . $data['id_entrainement'] . '</td>
<td>' . $data['intitule_entrainement'] . '</td>
<td>' . date("j/n/Y", strtotime($data['date_entrainement'])) . " " . date("G:i", strtotime($data['date_entrainement'])) . '</td>
<td><span class=" glyphicon glyphicon-plus" aria-hidden="true"></span></td>
</tr>
<tr class="exercicesHidden">
<td>1</td>
<td>' . $data['nom_exm'] . '</td>
<td>' . $data['reps'] . '</td>
<td>' . $data['poids'] . '</td>
<td>Up!</td>
</tr>
';
//echo '<tr class="exercicesHidden"><td>Coucou je suis caché!</td></tr>';
}
echo '
</tbody>
</table>
</div>'
I would like all the exercises are stored under one training, and when I click on it, it shows all the exercises from this training.
I hope I gave you all the things to help me to correct this problem!