Validation of Specific Date using Php or Javascript - php

Question

I need a quick way to validate in php or javascript whether a date is an invalid date such as (2/31 or 04/31 - since they dont exist), ALONG with if it is a LEAP year or not.
My code:
<?php
$month = $_POST["mo"];
$day = $_POST["theDay"];
$yr = $_POST["year"];
if (!isset($_POST['submit'])) { // if page is not submitted; echo form
?>
<h2 style="margin:0; padding:0;">Date Selection</h2>
<span style="color:gray; font-size:0.8em;">By Joseph Dickinson</span>
<FORM method="POST" action="<?php echo $PHP_SELF;?>">
<select name="mo">
<option disabled="disabled">SELECT MONTH</option>
<option>January</option>
<option>February</option>
<option>March</option>
<option>April</option>
<option>May</option>
<option>June</option>
<option>July</option>
<option>August</option>
<option>September</option>
<option>October</option>
<option>November</option>
<option>December</option>
</select>
<select name="theDay">
<option disabled="disabled">SELECT DAY</option>
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
<option>5</option>
<option>6</option>
<option>7</option>
<option>8</option>
<option>9</option>
<option>10</option>
<option>11</option>
<option>12</option>
<option>13</option>
<option>14</option>
<option>15</option>
<option>16</option>
<option>17</option>
<option>18</option>
<option>19</option>
<option>20</option>
<option>21</option>
<option>22</option>
<option>23</option>
<option>24</option>
<option>25</option>
<option>26</option>
<option>27</option>
<option>28</option>
<option>29</option>
<option>30</option>
<option>31</option>
</select>
<select name="year">
<option disabled="disabled">SELECT YEAR</option>
<option>2011</option>
<option>2010</option>
<option>2009</option>
<option>2008</option>
<option>2007</option>
<option>2006</option>
<option>2005</option>
<option>2004</option>
<option>2003</option>
<option>2002</option>
<option>2001</option>
<option>2000</option>
<option>1999</option>
<option>1998</option>
<option>1997</option>
<option>1996</option>
<option>1995</option>
<option>1994</option>
<option>1993</option>
<option>1992</option>
<option>1991</option>
<option>1990</option>
<option>1989</option>
<option>1988</option>
<option>1987</option>
<option>1986</option>
<option>1985</option>
<option>1984</option>
<option>1983</option>
<option>1982</option>
<option>1981</option>
<option>1982</option>
</select>
<INPUT TYPE="submit" value="Send" name="submit" />
</FORM>
<?
} else {
echo "You chose: " . " ". $month . " ".$day . ", ". $yr;
}
?>
If someone could please help me out here.

Answer 1

First, add numbers as values for months:
<select name="mo">
<option disabled="disabled">SELECT MONTH</option>
<option value="1">January</option>
<option value="2">February</option>
<option value="3">March</option>
<option value="4">April</option>
<option value="5">May</option>
<option value="6">June</option>
<option value="7">July</option>
<option value="8">August</option>
<option value="9">September</option>
<option value="10">October</option>
<option value="11">November</option>
<option value="12">December</option>
</select>
Then use checkdate():
<?php
$month = $_POST["mo"];
$day = $_POST["theDay"];
$yr = $_POST["year"];
if (checkdate($month, $day, $yr) !== true) {
// ?
}
?>
And if you want to do it in the browser as well, first add an onsubmit handler to the year form:
<FORM method="POST" action="<?php echo $PHP_SELF;?>" onsubmit="return checkLeap(this);">
Then your function:
function checkLeap(form) {
var month = form.mo.options[form.mo.selectedIndex].value;
var day = form.theDay.options[form.theDay.selectedIndex].value;
var year = form.year.options[form.year.selectedIndex].value;
if (month == 2 && day == 29 && (new Date(year,month,year).getDate() != 29)) {
alert('That is not a leap year. Please fix.');
return false;
}
return true;
}

Answer 2

When you create a timestamp with mktime() with a date too high for the month, it just skips up to the next month, with a date of the difference. For example, Feb 31 produces Mar 3. So to make sure it's valid, just create the time, and then re-check that the month hasn't changed.
$month = 2;
$date = 31;
$year = 2011;
$time = mktime(1, 0, 0, $month, $date, $year);
if (date('n', $time) != $month) {
// invalid error!
}
The same mechanism also automatically accounts for leap years. But if you want to know if it's a leap year or not, just check with date('L', $time);.
http://php.net/date
http://php.net/mktime
As a side note, if you do validate it with Javascript, you must also check with PHP. Never rely on client-side validation.