Run query for each checkboxes which are checked

Currently having a page where the admin can assign Contract from one worker to another worker.

My form (working)

<form id='form' name='form' method='POST' action='' style="width:80%!important;">
        <label for='ra'>From :</label>
        <SELECT name='ra' id='ra'>
            <OPTION value=''>
            <OPTION value={$res['idUtilisateur']}> {$res['USR_Login']}  //added with statement
        </SELECT>
        <br/><br/>
        <div id='devis'></div>
        <label for='toRA'>To :</label>
        <SELECT name='toRA' id='toRA'>
            <OPTION value=''>
            <OPTION value={$res['idUtilisateur']}> {$res['USR_Login']} //added with statement
        </SELECT>
    <input type='submit' name='submit' id='submit' value='Change'>
</form>

OPTION are added with sql statement, but I didn't display it.

When I select someone from my SELECT 'ra' (FROM), it displays all of his contracts in a table which checkboxes at each row which has the idContract for value and id.

My question is : How to manage my script.php to transfer every Contracts checked ?

My query would be :

UPDATE Contract
SET idUtilisateur = :idUser
WHERE idContract = :idContract

How to run it for each checkbox checked from my form ?

EDIT :
Table generating :

$(document).ready( function () { 
        $('#ra').change(function() {
            if($('#ra').val()) {
            $.ajax({ 
                type: "GET",
                url: "jsonDevisUtilisateur.php?ra=" + $('#ra').val(), 
                success: function(data) {
                        var table = "<table><tr><td>Numéro</td><td>Client</td><td>Site</td><td>Libellé</td><td></td></tr>"
                    for(var i=0; i<data.length; i++) {
                        table += "<tr><td>" + data[i].numDevis + "</td>";
                        table += "<td>" + data[i].client + "</td>";
                        table += "<td>" + data[i].site + "</td>";
                        table += "<td>" + data[i].libelle + "</td>";
                        table += "<td><input type='checkbox' value='"+data[i].id + "' name='"+data[i].id + "'></td></tr>"
                    }
                        table +="</table>";
                    document.getElementById('devis').innerHTML = table+"<br/><br/>";

                }       
            });
            } else document.getElementById('devis').innerHTML = "";
        });
    });