将多个<select>选项插入多行

I have a HTML form with a with multiple options, in which is possible to select multiple values (options).

I was using the implode, to INSERT the values in a MySQL table separated by a "," but now i need to change it. I've searched everywhere, but i don't seem to find any solution for my problem.

What i need to do, is to create different rows on form submit, with different values from the selected options.

I was using this previous code to insert into the table, the values separated by a "," .

$event = mysqli_real_escape_string($link, $_REQUEST['event']);
$date = mysqli_real_escape_string($link, $_REQUEST['date']);
$local = mysqli_real_escape_string($link, $_REQUEST['local']);
$disc = mysqli_real_escape_string($link, $_REQUEST['disc']);
$username_string = implode(', ', $_POST['username']);

$sql = "INSERT INTO events (event, date, local, disc, username) VALUES ('$event','".date('d-m-Y', strtotime($date))."', '$local', '$disc', '$username_string')";

And this is the HTML form i'm using.

    <form action="insert/insertEvents.php" id="newEvent" method="post">
               <div class="form-group">
                 <label for="user">Utilizador</label>
                 <br>
                 <select class="selectpicker" name="username[]" multiple>
                                                <?php
                                                    while ($row = mysqli_fetch_array($query2))
                                                    { echo ' 

                                                    <option>'.$row['username'].'</option>';

                                                    }
                                                ?>
                 </select>
               </div>
               <div class="form-group">
                 <label for="nameEvent">Evento</label>
                 <br>
                 <input type="text" name="event" class="form-control" id="event">
                 </div>
               <div>
               <label for="reportDate">Data</label>
                <br>
               <div class="bfh-datepicker">
               <div class="input-prepend bfh-datepicker-toggle form-group" data-toggle="bfh-datepicker">
               <span class="add-on"><i class="icon-calendar"></i></span>
               <input type="text" name="date" id="date" class="form-control">
            </div>
            <div class="bfh-datepicker-calendar">
              <table class="calendar table table-bordered">
              <thead>
              <tr class="months-header">
                <th class="month" colspan="4">
                   <a class="previous" href="#"><i class="icon-chevron-left"></i></a>
                   <span></span>
                   <a class="next" href="#"><i class="icon-chevron-right"></i></a>
                </th>
                <th class="year" colspan="3">
                    <a class="previous" href="#"><i class="icon-chevron-left"></i></a>
                   <span></span>
                   <a class="next" href="#"><i class="icon-chevron-right"></i></a>
               </th>
               </tr>
              <tr class="days-header"></tr>
           </thead>
           <tbody></tbody>
         </table>
       </div>
     </div>
   </div>
   <div class="form-group">
      <label for="namefat">Local</label>
     <br>
     <input type="text" name="local" class="form-control" id="local" placeholder="ex: Porto">
   </div>
   <div class="form-group">
        <label for="namefat">Descrição</label>
        <br>
        <textarea rows="12" name="disc" class="form-control" id="disc" form="newEvent"></textarea>
   </div>   
<button type="submit" class="btn btn-primary">Adicionar</button>
</form>

Can someone please explain me how should i solve this? I searched different questions from other users, and i couldn't find a question which i could identify myself with.

Do you want to insert all username?? Something like this?

//first remove your implode code
    foreach($_POST['username'] as $username){
         $sql = "INSERT INTO events (event, date, local, disc, username) VALUES ('$event','".date('d-m-Y', strtotime($date))."', '$local', '$disc', '$username')";
//call the insert query
    }