Php storing and updating birthdays

[keyboard]

In a registration form (html) I have an input for a birthday. I'm not sure what format I should store it in the sql database.

My sql dtabase looks like this

CREATE TABLE users(
id INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id),
username VARCHAR(30),
password VARCHAR(32),
level int(4) default '1',
suspended VARCHAR(5) default 'no',
firstname VARCHAR(30),
lastname VARCHAR(30),
day VARCHAR(30),
month VARCHAR(30),
year VARCHAR(30),
age VARCHAR(30),
gender VARCHAR(30),
email VARCHAR(30),
actor VARCHAR(30)) 

I need to be able to store their birthday, calculate their age (years) and update the age column to store the correct age once they have had a birthday.


Here's all the relevant code


My html form

<h1>Register an Account </h1> 
<font size="-5"><a href="../registerhelp" target="_blank">Why do I have to fill out this information?</a></font>
<br /><br />
<form action="check/checkedit.php" method="post" name="agreeform" >
  <div class="form_left">
Username:
  </div>
  <div class="form_right">
<input type="text" name="username" maxlength="60" />
  </div>
  <div class="clear"></div>
  <div class="form_left">
Password:
  </div>
  <div class="form_right">
<input type="password" name="pass" maxlength="20" />
  </div>
  <div class="clear"></div>
  <div class="form_left">
Confirm Password:
  </div>
  <div class="form_right">
<input type="password" name="pass2" maxlength="20" />
  </div>
  <div class="clear"></div>
  <div class="form_left">
First name:
  </div>
  <div class="form_right">
<input type="text" name="firstname" maxlength="15" />
  </div>
  <div class="clear"></div>
  <div class="form_left">
Last name:
  </div>
  <div class="form_right">
<input type="text" name="lastname" maxlength="20" />
  </div>
  <div class="clear"></div>
  <div class="form_left">

  Birthday:
  </div>
  <div class="form_right">
  <?php
// DAY
?>
<select name="day">
<?php
for ($i  = 1; $i < 32; $i++) {
  echo "  <option>$i</option>\n";
}
?>
</select>
  <?php
// MONTH
?>
<select name="month">
<option value="January" >January</option>
<option value="February" >February</option>
<option value="March" >March</option>
<option value="April" >April</option>
<option value="May" >May</option>
<option value="June" >June</option>
<option value="July" >July</option>
<option value="August" >August</option>
<option value="September" >September</option>
<option value="October" >October</option>
<option value="November" >November</option>
<option value="December" >December</option>
</select>

  <?php
 // YEAR
 ?>
 <?php
$maxyear = date("Y");
$eighty = "82";
$minyear = $maxyear-$eighty; 
?>

<select name="year">
<?php
for ($f  = $maxyear; $f > $minyear; $f--) {
  echo "  <option>$f</option>\n";
}
?>
</select>
  
  
  </div>
  <div class="clear"></div>
  <div class="form_left">
  
Gender:
  </div>
  <div class="form_right">
<input type="radio" name="gender" value="Male" id="Male">Male

<input type="radio" name="gender" value="Female" id="Female">Female
  </div>
  <div class="clear"></div>
  <div class="form_left">
E-mail:
  </div>
  <div class="form_right">
<input type="text" name="email" maxlength="30" />
  </div>
  <div class="clear"></div>
  <div class="form_left">
What type of work are you interested in?

  </div>
  <div class="form_right">

  <!--
<input type="radio" name="shade" value="Actor" id="actor" onclick="chgType()">Actor 

<input type="radio" name="shade" value="Backstage" id="backstage" onclick="chgType()">Backstage worker

<input type="radio" name="shade" value="Both" id="both" onclick="chgType()">Both<br />
-->

<input type="radio" name="shade" value="Actor" id="actor">Acting

<input type="radio" name="shade" value="Backstage" id="backstage">Backstage work

<input type="radio" name="shade" value="Both" id="both">Both<br />

<!--
<select name="typeSelector" id="typeSelector" style="visibility: hidden">
<option>Set mover</option>
<option>Sound</option>
</select>
-->

  </div>
  <div class="clear"></div>
  <div class="form_left">&nbsp;</div>
  <div class="form_right">
<input type="submit" name="submit" value="Send!" />
  </div>
  <div class="clear"></div>
</form>

The processing page

<body>

<?php
require "../../database.php";


 // This code runs if the form has been submitted
 if (isset($_POST['submit'])) { 

 // This makes sure they did not leave any fields blank
 if (!$_POST['username'] | !$_POST['pass'] | !$_POST['pass2'] | !$_POST['firstname'] | !$_POST['lastname'] |  !$_POST['day'] | !$_POST['month'] | !$_POST['year'] | !$_POST['gender'] |  !$_POST['email'] )  
     {

         die('You did not complete all of the required fields <br /><br /> <a href=../registeredit.php>Back</a> ');
     }

 // checks if the username is in use
     if (!get_magic_quotes_gpc()) {
         $_POST['username'] = addslashes($_POST['username']);
     }
 $usercheck = $_POST['username'];
 $check = mysql_query("SELECT username FROM users WHERE username = '$usercheck'") 
or die(mysql_error());
 $check2 = mysql_num_rows($check);

 //if the name exists it gives an error
 if ($check2 != 0) {
         die('Sorry, the username '.$_POST['username'].' is already in use. <br /><br /> <a href=../registereit.php>Back</a>');
                 }

 // this makes sure both passwords entered match
     if ($_POST['pass'] != $_POST['pass2']) {
         die('Your passwords did not match. <br /><br /> <a href=../>Back</a> ');
     }

     // here we encrypt the password and add slashes if needed
     $_POST['pass'] = md5($_POST['pass']);
     if (!get_magic_quotes_gpc()) {
         $_POST['pass'] = addslashes($_POST['pass']);
         $_POST['username'] = addslashes($_POST['username']);
             }
if($_POST[firstname] != '' && $_POST[firstname] != '' && $_POST[firstname] != '' && $_POST[firstname] != '') {
 // now we insert it into the database
 /*
 //Check if typeSelector is set.
if($_POST[shade] == 'Backstage' || $_POST[shade] == 'Both') {  

$type = $_POST[typeSelector];
} else {
$type = $_POST[shade];
}  
*/
$type = $_POST[shade];

// CALCULATING AND STORING THEIR AGE

$day = $_POST[day];
$month = $_POST[month];
$year = $_POST[year];


 
 
     $insert = "INSERT INTO users (username, password, firstname, lastname, day, month, year, gender, email, actor)
             VALUES ('".$_POST['username']."', '".$_POST['pass']."', '$_POST[firstname]', '$_POST[lastname]', '$day', '$month', '$year', '$_POST[gender]', '$_POST[email]', '$type')";
     $add_member = mysql_query($insert);

     echo <<<EOF
     <h1>Registered</h1>
 <p>Thank you, you have registered - you may now login</a>.</p>
EOF;

     } else {
         echo "Please fill in all of the required fields.";
     } 

 } 
 else 
 {    
 ?>


 <?php
 }
 ?>

This is the bit

// CALCULATING AND STORING THEIR AGE

$day = $_POST[day];
$month = $_POST[month];
$year = $_POST[year]; 

Any help would be great!

[keyboard]

Anybody???