PHP & Javascript for dynamic select menus

adrocker55

OK...now, I understand that Javascript cannot talk to PHP, or at least thats what I have gathered from reading numerous posts lately. I want to do the following:

I have I dropdown menu that contains all the months, values being 1-12. I have a second dropdown that contains day values.

Currently, I am using some php date functions to populate these option values dynamically (based on the date value of some variables sent from the previously clicked-on page), but only for the date originally selected. If you want to change the month value, the day value does not change. I would like the day values to be dependent on the month value that is currently selected, and so my first reaction was to use an onChange="some_function()" in the month select menu. Thing is, if I use Javascript to change the day values based on the month value selected, I run into the static value problem with leap years and all that crap. I can't just define preselected day values for each month value, if I did it would be incorrect once a leap year comes around.

Anyways, getting to the point, what would be the best way to do this??? I would LOVE to be able to just tell Javascript to set the PHP variable $month value to the selected months value! So, PLEASE help....someone....

And, I really do appreciate anyones help, last time I posted something I got absolutely no response...I don't understand why, I cant imagine that you ppl out there at PHPbuilder.com can't help me at all!!!

Please!!! PLEASE!!!!

Here is my code:


<select name="StartDateMonth" class="orangeform" onChange="repop()">
<? for($i = 1; $i <= 12; $i++){ ?>
<option value="<?  echo $i ?>" <? if($i == $month){ echo "selected"; }?>> 
<?  echo date("F", mktime(0, 0, 0, $i, 1, $year)) ?>
</option>
<? } ?>
</select> <select name="StartDateDay" class="orangeform">
<? for($i = 1; $i <= $month_days; $i++){ ?>
<option value="<?  echo $i ?>" <? if($i == $day){ echo "selected"; }?>> 
<?  echo $i ?>
</option>
<? } ?>
</select>

This code is just what I currently have setup to populate the option values based on the date value passed from the previously clicked-on page.

What to do to make the month value change the options in the day select box? I don't know!!!!

PLEASE HELP ME!!!!

Sincerely,

The chick who needs anyones help with this one...

sarahk

ok..

first, javascript can talk to php if it sets a hidden (or visible) field and submits a form

second, php can talk to javascript, for instance it can set up an array of months and days for the javascript to use, problem is it will only be valid for the current year.
PHP just spits out html which the javascript can read if within <script> tags. javascript doesn't know or care if it's code was generated dynamically on the server or is a static page.

However, you need to balance the need for client side and server side processing. Having to submit after every change is a drag.

You will find plenty of people here who believe that the only reliable processing is server side and they make some valid points. However a great many professional sites use a careful balance of both and I think we can take their example. Be warned however that the professional sites have time and $ resources to ensure that the whole thing is solid and you might not.

adrocker55

So, what is it that I should do to make this happen? I guess as long as the year value is set on the page that will not change, the chances of that are slim-to-none, and december and january both have 31 days! so that eleviates that problem...

That means that I could tell Javascript the month length values for each month based on the month selected using PHP to predfine in Javascript what each month values should be...That way if the year changes and its a leap year, it wont matter since the year will stay the same regardless? well, I guess I could try something like that...

About the iframes tho...I saw your reply to another similar issue, could you tell me more about how something like that would work?

sarahk

iframes don't have to be visible but you can use javascript to set values and submit(). The iframe then runs off to php to do it's stuff and comes back.

You know what, I reckon I might write a wee tutorial on this. Watch this space...

icq me if you want

sarahk

check out some stuff I've chucked up at http://property.digitalrice.com/muck/example.html

I'll turn it into a proper tutorial later and I've put the code up so it should point you in the right direction.

adamgeorge

Can't you just use JavaScript to get the current date, check whether it's a leap year or not, and then based on that populate the select boxes with the appropriate number of elements?

Everytime a user changes the month, you call a JavaScript function that checks the current date, and makes sure that there is only the appropriate days for the current year and the selected month.

Hope that helps,
-Adam 🙂