ตอน input ข้อมูล อยากให้จำค่า $_SESSION ไว้ใช้ค่านี้ในหน้าอื่น ๆ อย่างไรค่ะ

$sssss1 = $_POST['quotation_discount'];
$_SESSION['SD'] = $sssss1;

				<div class="form-group">
        			<label for="quotation_discount" class="col-sm-2 control-label">ส่วนลด (%)</label>
                                <div class="col-sm-10">
                                  <input type="number" class="form-control" name="quotation_discount"  value="<?php $quotation_discount = $_POST['quotation_discount'];?>" id="quotation_discount" placeholder="ส่วนลด(%)">
                                </div>
                            	</div>  

                            <?php
				$_SESSION['quotation_discount'] = $quotation_discount;
     			    ?>

<?php
session_start();
$_SESSION["strName"] = "Mr.Weerachai Nukitram";
$_SESSION["strSiteName"] = "ThaiCreate.Com";
session_write_close();
?>

$id = $_SESSION['id'];

<input type="text" name="txtname" value="<?php echo $id;?>">

<form>
<input name=abc >
<button type=submit>submit</button>

<?php session_start(); // ขาดไม่ได้
$abc=isset($_POST['abc']) ? filter_input(INPUT_POST, 'abc') : '';

$_SESSION['abc']=$abc;