correct write the second query

I have a big problem because I don’t know how to correctly write the second query. I ask for help.

The table vt_personale has

user_nome 
user_cognome 
user_postazione 
user_coordinatore

The table vt_formaz_corsi has

user_nome (the same of vt_personale but split user_nome e user_cognome) 

and other values

<div class="card-datatable table-responsive pt-0  p-3 w-100" > 
    <table id="emp-table" class="datatables-basic table table-bordered  p-3 w-100" width="100%">
        <thead> 
            <tr>
                <th>Cognome Nome</th>
                <th>Postazione</th>
                <th>Coordinatore</th>
                <th style="max-width:220px">Corso</th>
                <th>Tipo</th>
                <th>Ultimo corso</th>  
                <th>Scadenza</th>
                <th></th>
                <th></th>
            </tr> 
            <tr>
                <th>Cognome Nome</th>
                <th>Postazione</th>
                <th>Coordinatore</th>
                <th style="max-width:220px">Corso</th>
                <th>Tipo</th>
                <th>Ultimo corso</th>
                <th>Scadenza</th>
                <th></th>
                <th></th>
            </tr>
        </thead>
        <tfoot>
            <tr>
                <th>Cognome Nome    </th>
                <th>Postazione</th>
                <th>Coordinatore</th>
                <th style="max-width:220px">Corso</th>
                <th>Tipo</th>
                <th>Ultimo corso</th>
                <th>Scadenza</th>
                <th></th>
                <th></th>
            </tr>
        </tfoot>
        </thead>
        <tbody class="table-border-bottom-0" id="myTable">
            <?php  $num = 0;
            include_once 'main.php';
            $stmt = $DB_con->prepare('SELECT * FROM vt_formaz_corsi ORDER BY user_nome ASC');
            $stmt->execute();
            $Count= $stmt->rowCount();
            if($stmt->rowCount() > 0){
                while($row=$stmt->fetch(PDO::FETCH_ASSOC)){
                extract($row);
            ?>
                <tr>
                    <td class="center"><?php echo $row['user_nome']; ?></td>
                    <?php  // this is the second query that not read
                    $stmtpersonale = $DB_con->prepare("SELECT *  FROM vt_personale as P  INNER JOIN vt_formaz_corsi as C WHERE CONCAT_WS(P.user_cognome, ' ', P.user_nome) = '.(string)$row['user_nome'].'");
                    $stmtpersonale->execute(); $Countpers= $stmtpersonale->rowCount();
                    if($stmtpersonale->rowCount() > 0) {
                    while($row4=$stmtpersonale->fetch(PDO::FETCH_ASSOC)){
                    extract($row4); 
                    ?>
                    <td class="center"><?php echo $row4['user_postazione']; ?></td>
                    <td class="center"><?php echo $row4['user_coordinatore']; ?></td>
                    <?php  } } ?>
                    <td class="center  p-3 w-100" style="width:50%"><?php echo $row['user_corso']; ?></td>
                    <td class="center"><?php echo $row['user_residenziale']; ?></td>
                    <td class="center"><?php echo $result; ?></td>
                    <td class="center"> <?php echo $resultscadenza;?></td>
                    <td class="center"> <?php echo $$differenza;?></td>
                </tr>
            <?php } }else{?>
                    <div class="col-xs-12">
                    <div class="alert alert-warning"><span class="glyphicon glyphicon-info-sign"></span> &nbsp; Nessun dato trovato ... </div>
                    </div>
            <?php}?>
            <?phpob_end_flush();?>
        </tbody> 
    </table>  
</div>