I just wrote this PHP/HTML code. Perhaps it can help you:
<html>
<head>
<title>Age Calculator</title>
</head>
<body>
<H3>Enter your birth date:</H3>
<form action="<?php echo $_SERVER["PHP_SELF"]; ?>" method="POST">
<p><strong>MM:</strong>
<input type="text" name="month" size="2" maxlength="2" />
<strong>DD:</strong>
<input type="text" name="day" size="2" maxlength="2"/>
<strong>YYYY:</strong>
<input type="text" name="year" size="4" maxlength="4"/></p>
<p><input type="submit" value="Calculate age!"/></p>
</form>
</body>
</html>
<?php
if ( isset( $_POST["month"] ) )
{
$bmonth = intval( $_POST["month"] );
$bday = intval( $_POST["day"] );
$byear = intval( $_POST["year"] );
$date1 = time();
$date2 = mktime( 0, 0, 0, $bmonth, $bday, $byear );
$dateDiff = $date1 - $date2;
$fullDays = floor($dateDiff/(60*60*24));
$fullHours = floor(($dateDiff-($fullDays*60*60*24))/(60*60));
$fullMinutes = floor(($dateDiff-($fullDays*60*60*24)-($fullHours*60*60))/60);
$years = floor( $fullDays / 365 );
$months = ceil( $fullDays % 365 / 30 );
if ( $date2 == false )
{
$message = "Invalid birth date given; must be greater than 12/14/1901.";
}
else if ( $years == 0 )
{
$message = "Your approximate age is $months month(s).";
}
else
{
$message = "Your approximate age is $years year(s) and $months month(s).";
}
echo "$message<br/>";
}
?>