How to insert values of multiple select - php

Question

I have a list multiple select, this is the code :
<form method="post" action="">
<select name=thematique[] multiple>
<option value="1"> MIE </option>
<option value="2"> Migration </option>
<option value="3"> Réunification familiale </option>
</select>
<button type="submit" class="button" name="categoriser">Catégoriser</button>
</form>
My problem is if I select MIE + Migration + Réunification familiale, so I have 3 lines in my data base for the same ID.
I want to have one line which will insert all options of the select (0 1 2 or 3).
$id_struct=$_POST['id_struct'];
$thematique=$_POST['thematique']);
foreach($thematique as $item) {
$string= $item.' ';
echo $string;
$bdd->exec("INSERT INTO categorisation SET id_thematique=$string
WHERE id_struct=$id_struct");
}
PS : id_thematique is a foreign key.

Answer 1

1)
You need to add VALUE attribute in your select box .
2) Don't treated INSERT query AS UPDATE query
Your select box
<select name=thematique[] multiple>
<option value="MIE"> MIE </option>
<option value="Migration"> Migration </option>
<option value="Reunification_familiale"> Reunification familiale </option>
</select>
Your php file for insert into three separate field
<?php
foreach ($_POST['thematique'] as $thematique)
{
///your insert code//
$bdd->exec("INSERT INTO categorisation (`thematique`) VALUES ('".$thematique."'");
}?>

Answer 2

You can use array of you thematique as object array:
$thematiqueArray = array(0=>'MIE', 1=>'Migration', 2=>'Réunification familiale');
set your html options element like this:
<option value=0>MIE</option>
<option value=1>Migration</option>
<option value=2>Réunification familiale</option>
and on your POST catching similiar like this:
$thematique=$_POST['thematique']);
foreach($thematique as $key => $value) {
$item = $thematiqueArray[$key];
echo $item;
}

Answer 3

One solution would be to give base2 values to your select. Like 1,2,4,8 etc... then you can sum the selected values up, and know which are selected. But this only works if you don't need the values in other places.