Problème de requête erreur de syntaxe

Bonjour je rencontre un problème lors du requête

voici le message d'erreur:

Fatal error: Uncaught PDOException: SQLSTATE[42000]: Syntax error or access violation: 1064 Erreur de syntaxe près de '' à la ligne 9 in D:\wamp64\www\#\models\BetModel.php on line 10
( ! ) PDOException: SQLSTATE[42000]: Syntax error or access violation: 1064 Erreur de syntaxe près de '' à la ligne 9 in D:\wamp64\www#\models\BetModel.php on line 10

Ma requête ("Fonctionne dans phpmyadmin")

<?php

function lastBetsClosed()
{
    $db = dbConnect();
    $req = $db->query('SELECT user_id ,event,null AS event_1,null AS event_2,null AS event_3,null AS event_4,sport,null AS sport_1,null AS sport_2,null AS sport_3,null AS sport_4,date_event,null AS date_event_1,null AS date_event_2,null AS date_event_3,null AS date_event_4,hour_event,null AS hour_event_1,null AS hour_event_2,null AS hour_event_3,null AS hour_event_4,type,cost,null AS cost_1,null AS cost_2,null AS cost_3,null AS cost_4,stake,prognosis,null AS prognosis_1,null AS prognosis_2,null AS prognosis_3,null AS prognosis_4,competition,null AS competition_1,null AS competition_2,null AS competition_3,null as competition_4,result
    FROM bet_simple 

    UNION 

    SELECT user_id,null AS event,event_1,event_2,event_3,event_4,null AS sport,sport_1,sport_2,sport_3,sport_4,null AS date_event,date_event_1,date_event_2,date_event_3,date_event_4,null AS hour_event,hour_event_1,hour_event_2,hour_event_3,hour_event_4,type,cost,cost_1,cost_2,cost_3,cost_4,stake,null AS prognosis,prognosis_1,prognosis_2,prognosis_3,prognosis_4,null as competition,competition_1,competition_2,competition_3,competition_4,result
    FROM bet_combi 

    UNION ');
    return $req;
}

Voici le code avec la boucle :

<?php

while ($data = $bets->fetch()) {
?>
<tr>

<td>
<?= getUsername($data['user_id']); ?>
</td>
<td>
<?= getIconSport($data['sport'], $data['type']); ?>
</td>
<td>
<?=
$data['event']

?>
</td>
<td>
<?= $data['date_event'] ?>
</td>
<td>
<?= $data['prognosis'] ?>
</td>
<td>
<?= $data['cost'] ?>
</td>
<td>

</td>
<td>
<?php getGainBet($data['stake'], $data['cost'], $data['result']); ?>

</td>
<td>

<?php getIconResult($data['result']); ?>

</td>
</tr>
<?php
}
$bets->closeCursor();
?>

EDIT : Ajout du LANGAGE dans les balises de code pour avoir la coloration syntaxique.
Explications disponibles ici: https://codes-sources.commentcamarche.net/faq/11288-les-balises-de-code