Multiple Checkbox

A question about Checkbox.
How to mark several checkboxes and enter their values ​​into the database, all selected in one cell?
After all, only the first value is added.

<label>
  <input type="checkbox" name="den" value="" id="CheckboxGroup1_0" />
  </label>
<br />
<label>
  <input type="checkbox" name="den" value="" id="CheckboxGroup1_1" />
  </label>
<br />
<label>
  <input type="checkbox" name="den" value="" id="CheckboxGroup1_2" />
  </label>

.

$result = mysql_query("INSERT INTO students (den) VALUES ('$den')");
    if ($result == 'true') {echo "!";}
    else {echo "!";}

Answer 1, authority 100%

Name the buttons not den, but den[], then in the incoming $den you will get an array of values, add them one by one (foreach).


Answer 2, authority 17%

The server receives the den[] array to write all the values ​​into one cell, you need to concatenate them before inserting, for example, like this:

$joined_den = join(",", $den);