Testing Input

Here is the backend code of the page:
    <?php
        if(isset($_POST['text']))
        {
            echo '<div class="alert alert-success"><b>Thanks we have recieved your message!</b>'
            echo '<hr/>'.$_POST['text'].'</div>';
        }
    ?>
    <form method="post">
        <div class="form-group">
        <label><b>Input test Text:</b></label>
        <textarea type="text" required name="text" class="form-control"></textarea>
        </div>
        <input type="submit" value="send" class="btn btn-primary"/>
    </form>

The below form is designed for testing.
Please submit the form with different input and note the result.
Example Input Value : هشت سمستر تحصیلی را در قلب رنا سپری کردید

This input value makes problem while submitting the form