PHP - Sesiones con PHP

<?php

require 'conexion.php';

session_start();

$usuario = $_POST['email'];

$clave = $_POST['password'];

$q = "SELECT COUNT(*) as contar FROM pe_home WHERE mail_h = '$usuario' and psw_h = '$clave'";

$consulta = mysqli_query($conexion,$q);

$array = mysqli_fetch_array($consulta);

if($array['contar']>0){

	$_SESSION['username'] = $usuario;

	header("location: homestay/index.php");

}else{

	echo "datos incorrectos";

}

?>

<?php

require '../loguear.php';

session_start();

$usuario = $_SESSION['username'];

// Conexion a la base de datos

require_once('bdd.php');

if (isset($_POST['title']) && isset($_POST['start']) && isset($_POST['end']) && isset($_POST['color']) && isset($_SESSION['username']) ){

	$title = $_POST['title'];

	$start = $_POST['start'];

	$end = $_POST['end'];

	$color = $_POST['color'];

	$sql = "INSERT INTO events(title, start, end, color, email) values ('$title', '$start', '$end', '$color', '$usuario')";

	$query = $bdd->prepare( $sql );

	if ($query == false) {

	 print_r($bdd->errorInfo());

	 die ('Erreur prepare');

	}

	$sth = $query->execute();

	if ($sth == false) {

	 print_r($query->errorInfo());

	 die ('Erreur execute');

	}

}

header('Location: '.$_SERVER['HTTP_REFERER']);

?>

$(document).ready(function() {

    var date = new Date();

   var yyyy = date.getFullYear().toString();

   var mm = (date.getMonth()+1).toString().length == 1 ? "0"+(date.getMonth()+1).toString() : (date.getMonth()+1).toString();

   var dd  = (date.getDate()).toString().length == 1 ? "0"+(date.getDate()).toString() : (date.getDate()).toString();

    $('#calendar').fullCalendar({

        header: {

             language: 'en',

            left: ' prev,today,next ',

            center: 'title',

            right: 'basicWeek,month',

        },

        defaultDate: yyyy+"-"+mm+"-"+dd,

        defaultView: 'month',

        firstDay: 1,

        editable: true,

        eventLimit: true, // allow "more" link when too many events

        selectable: true,

        selectHelper: true,

        select: function(start, end) {

            $('#ModalAdd #start').val(moment(start).format('YYYY-MM-DD HH:mm:ss'));

            $('#ModalAdd #end').val(moment(end).format('YYYY-MM-DD HH:mm:ss'));

            $('#ModalAdd').modal('show');

        },

        eventRender: function(event, element) {

            element.bind('dblclick', function() {

                $('#ModalEdit #id').val(event.id);

                $('#ModalEdit #title').val(event.title);

                $('#ModalEdit #color').val(event.color);

                $('#ModalEdit').modal('show');

            });

        },

        eventDrop: function(event, delta, revertFunc) { // si changement de position

            edit(event);

        },

        eventResize: function(event,dayDelta,minuteDelta,revertFunc) { // si changement de longueur

            edit(event);

        },

        events: [

        <?php foreach($events as $event):

            $start = explode(" ", $event['start']);

            $end = explode(" ", $event['end']);

            if($start[1] == '00:00:00'){

                $start = $start[0];

            }else{

                $start = $event['start'];

            }

            if($end[1] == '00:00:00'){

                $end = $end[0];

            }else{

                $end = $event['end'];

            }

        ?>

            {

                id: '<?php echo $event['id']; ?>',

                title: '<?php echo $event['title']; ?>',

                start: '<?php echo $start; ?>',

                end: '<?php echo $end; ?>',

                color: '<?php echo $event['color']; ?>',

            },

        <?php endforeach; ?>

        ]

    });

    function edit(event){

        start = event.start.format('YYYY-MM-DD HH:mm:ss');

        if(event.end){

            end = event.end.format('YYYY-MM-DD HH:mm:ss');

        }else{

            end = start;

        }

        id =  event.id;

        Event = [];

        Event[0] = id;

        Event[1] = start;

        Event[2] = end;

        Event[3] = id_home;

        $.ajax({

         url: 'editEventDate.php',

         type: "POST",

         data: {Event:Event},

         success: function(rep) {

                if(rep == 'OK'){

                    alert('Event saved');

                }else{

                    alert('Try Again');

                }

            }

        });

    }

});

$sql = "SELECT id, title, start, end, color FROM events ";

$req = $bdd->prepare($sql);

$req->execute();

$events = $req->fetchAll();

$sql = "SELECT id, title, start, end, color FROM events WHERE email =" . $_SESSION['username'];