即使在表单已经提交到我的PHP后，仍然保留在下拉列表中选择的值

<?php

?>

/* Array to store days in a week*/
 $NoofDays=array("Monday","Tuesday","Wednesday","Thurseday","Friday","Saturday","Sunday");

?>
<div class="form-wrapper">
<form action=""  method="post">
     <select name="days">
         <?php foreach($NoofDays as $days){?>

        <option <?php if( $daysTitle== '$days')?> selected="selected"> <?php echo $days;?></option>

        <?php } ?>
    </select>
    <button type='submit' class="btn">Submit me</button>
</form>`enter code here`
  </div>
<?php
/* Script to generate the Switch case */
    if (isset($_POST['days'])) {
        $selected = $_POST['days'];


    switch ( $selected) {
        case "Monday":
            echo "Laugh on Monday, Laugh for danger";
            break;
        case "Tuesday":
            echo "Laugh on Tuesday, Laugh for stranger";
            break;
        case "Wednesday":
            echo "Laugh on Wednesday,Laugh for Letter";
            break;
            case "Thurseday":
            echo " Laugh on Thurseday,Something better";
            break;
            case "Friday":
            echo "Laugh on Friday,Laugh for sorrow";
            break;
            case "Saturday":
            echo "Laugh on Saturday,Joy Tommorow!";
            break;

        default:
            echo "Laugh on Every day for some reason:)";
    }
        }
?>
<?php

?>

/* Array to store days in a week*/