Ajax not working?

Posted on 2014-01-28
Last Modified: 2014-01-28

Please see attached php files; the first one (ajax_test.php) is supposed to take the name selected from the pulldown & look it up in a corresponding table on the web server. Try running it at It returns nothing (or if it does, I can't seem to detect how to see it).

Note I DO NOT want the result displayed directly on the page; I will use it for something else.

I suspected that the server program was at fault so I tried it directly using (I know that name is in the database). It worked properly.

What's wrong?

You may wonder why I am trying this; this is just to see if I can do it like this, the real application will be more complex.

Question by:Richard Korts
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LVL 58

Expert Comment

ID: 39815694
Seems to be working fine for me.
What makes you think it is not working?

Author Comment

by:Richard Korts
ID: 39815709
To Cathal,

Note the Javascript function show_sel which is run onLoad; it does not run when the server process is completed. Or maybe that is not an "onLoad"?

LVL 15

Expert Comment

ID: 39815717
if (xmlhttp.readyState==4 && xmlhttp.status==200)

it would not run onLoad as you have already loaded your page and later operation is performed.
You have to call the function explicitly
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LVL 34

Accepted Solution

Slick812 earned 500 total points
ID: 39815796
greetings  rkorts, ,  You have very many things of Code in your ajax setup (browser and server side code) that are incorrect or just barely functional, I would think the Main Problem is this line of code in JS -

as a Javascript technicality the FORM inputs as a -
<input type="hidden" name="txtHint" id = "txtHint">
 do NOT have any innerHTML , as an Input it has a "value" that can be read or write to, SO, this may can work -

also in your Ajax connection you have some simple altervives -
     xmlhttp=new XMLHttpRequest();
     xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");

these really need to be in  javascript  "try" catch blocks, because in a few browsers there may be problems and no connection is made.

AND  for page development and testing, you need to have a visible PAGE output to tell you what is returned from the AJAX request, so you know that the correct response is being retrieved, otherwise you are Blind to what's happening and ask questions here on experts, just to get some idea what it does, as you say - "I can't seem to detect how to see it"
Can help with ajax code if you need that, HOWEVER, there are a thousand javascript Ajax add-on and librarys that do Ajax, and are fully tested.
But you really do not even need to do any AJAX, for this as you already have the First and Last names in the SELECT, all you have to do is use JS to change the value of the hidden input to the names from the select.
Ask questions if you need more information!
LVL 110

Expert Comment

by:Ray Paseur
ID: 39815834
The "modern" approach to AJAX is to use jQuery (since about 2005).  This article teaches the basics.

And the code you have in there is ripe for getting your database clobbered.  You'll need to get off of MySQL anyway, since PHP is doing away with MySQL support.  This article explains why and what you must do to keep your scripts running in the future.
LVL 43

Expert Comment

by:Chris Stanyon
ID: 39815835
May not help you out on this problem, but the way you are coding is 'old-school'.

In your PHP script you are using the deprecated mysql functions (you need to switch to mysqli or PDO)

For doing this kind of thing, unless you can come up with a very good reason not to, start using jQuery. Running AJAX scripts using jQuery, your whole javascript code becomes 2 or 3 lines of code - robust, clean and fully cross-browser compliant.

And just for my own curiousity - why on earth are you targetting IE5 and IE6!!
LVL 43

Expert Comment

by:Chris Stanyon
ID: 39815837
haha - Ray - at least we're on the same wavelength :)

Author Comment

by:Richard Korts
ID: 39815885
To all,

With the exception of 1 or two lines, I copied the sample ajax code from a sample given at w3 schools. I have no clue about why they are concerned about IE5 & 6.

I am aware of the MySQL issue. Thank you for pointing that out.

I figured out a way to do what I need without going back to the server with Ajax.
LVL 110

Expert Comment

by:Ray Paseur
ID: 39816097
I have no clue about why they are concerned about IE5 & 6.
It's because their code example is many years out of date.  And now that you've copied it, you've made your code many years out of date, too.  Copying the code without understanding the code is AntiPractice #1!

Next time before you copy something you don't understand, stop by EE and ask if it's a good idea to use that example, or if there is a better example available.  We have a lot of articles here that can help you keep things up-to-date, follow best practices, etc.

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