如何删除复选框的PHP通知？

Question

When I submit form without selecting input type=check box , the NOTICE will appear so please tell me how to avoid it? I ask it because when I do with input type=text , the NOTICE doesn't appear.

<?php
if(isset($_POST['submit'])) {
    echo $_POST['check'];
}
?>
<form action="" method="post">
    <input type="check box" name="check" value="1">
    <input type="submit" name="submit">
</form>

Answer 1

empty() checks variable is set or not and also it has any value both...

  <?php

    if(!empty($_POST['submit'])) {
       echo  $checkbox_value = !empty($_POST['check'])?$_POST['check']:'--';
    }
    ?>