Find day of the week with PHP - Printable Version

PHP Code:
<html>
<head>
<title>Birthday Calculator</title>
<style type="text/css"> 
.text {
color: #000000;
font-family: "Trebuchet MS";
}
</style>
</head>
<body>
<form method="get" action="">
    <span class="text">Date:</span>
    <select name="date" class="text">
        
        <option value=""></option>
    <?php
    for($i=1;$i<=31;$i++)
    {
        ?>
        
        <option value="<?php echo $i; ?>"<?php if($_GET['date'] == $i) { echo " selected=\"selected\""; } ?>><?php echo $i; ?></option>
        <?php
    }
    ?>
    
    </select>
    <?php
    $months = array("1" => "January",
                    "2" => "February",
                    "3" => "March",
                    "4" => "April",
                    "5" => "May",
                    "6" => "June",
                    "7" => "July",
                    "8" => "August",
                    "9" => "September",
                    "10" => "October",
                    "11" => "November",
                    "12" => "December"
                    );
    ?>
<span class="text">Month:</span>
    <select name="month" class="text">
        
        <option value=""></option>
        <?php
        foreach($months as $mid => $month)
        {
            ?>
        
        <option value="<?php echo $mid; ?>"<?php if($_GET['month'] == $mid) { echo " selected=\"selected\""; } ?>><?php echo $month; ?></option>
            <?php
        }
        ?>
        
    </select>
    <span class="text">Year:</span>
    <select name="year" class="text">
        
        <option value=""></option>
    <?php
    for($i=2009;$i>=1900;$i--)
    {
        ?>
        
        <option value="<?php echo $i; ?>"<?php if($_GET['year'] == $i) { echo " selected=\"selected\""; } ?>><?php echo $i; ?></option>
        <?php
    }
    ?>
    
    </select>
    <input type="submit" class="text" value="Submit" />
</form>
<?php
if($_GET)
{
    foreach($_GET as $key => $val)
    {
        $_GET['$key'] = htmlspecialchars($val);
    }
    $day_of_week = date("l", mktime(0, 0, 0, $_GET['month'] , $_GET['date'] , $_GET['year']));
    echo "<span class=\"text\">You were born on a " . $day_of_week . "</span>";
}
?>
</body>
</html>