PHP script not echoing data when called via AJAX

Question

I have been staring at this problem for the past 2 hours and can't seem to fathom it, even after validating that everything loads correctly when scouring the console.

I basically have two sliders on my page which will eventually populate results in a table, every time I change my slider I send an array of two values to my AJAX script:

function update_results(values) 
{
   $.ajax({
       type: "GET",
       url:  "./app/core/commands/update_results.php",
       data: { query : values },
       cache: false,
       success: function(data) {
                   // eventually some success callback
       }
   });
}

The browser successfully finds update_results.php but it does not perform the logic on the page ( I assume it has found the page as the 404 error does not appear in my console. )

At this point in time the script is extremely bare-bones as I'm obviously trying to establish communication between both files:

<?php
$vals = $_GET['values'];
echo $vals;

In this case $vals is never echoed to the page, am I missing something in my AJAX? I know the values enter the function as alerted them out before attaching the PHP script.

If $_GET['values'] is an array, you cannot echo it. To check if it is, use console.log(values); before the ajax. — Al.G.
– Al.G., Commented Jun 14, 2014 at 12:28
@Ididn'tunderstand... I've tried console logging and var_dump() but neither work — Halfpint
– Halfpint, Commented Jun 14, 2014 at 12:29

dognose · Accepted Answer · 2014-06-14 12:47:59Z

2

Ajax Calls are suffering from Browser Cache. If your browser thinks, that he already knows the content of update.php, he will return the cached content, and not trigger the script. Therefore your modified code might simply not get executed. (Therefore your insert query wasn't executed)

To ensure this is not happening in your case, it is always a good idea to pass a parameter (timestamp) to the script, so your browser thinks it's another outcome:

function update_results(values) 
{
   $.ajax({
       type: "GET",
       url:  "./app/core/commands/update_results.php?random_parameter=" + (new Date().getTime());
       data: { query : values },
       cache: false,
       success: function(data) {
                   // eventually some success callback
       }
   });
}

This will ensure that - at least - the browser cache is refreshed once per second for update_results.php, no matter what browser cache-settings or server-side cache advices are telling.

edited Jun 14, 2014 at 12:47

answered Jun 14, 2014 at 12:36

dognose

21k9 gold badges67 silver badges108 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

Halfpint Over a year ago

interesting, I never knew that, I thought by setting cache to false I would bypass that sort of behavior - that would explain why I've been experiencing an undefined index error the past 10 mins, due to one side being GET and the other POST!

dognose Over a year ago

@AlexSims Never trust any programatic cache advice. Settings might override it, Server-side advices might simply be ignored. This might not solve your problem - it just makes SURE, that the code you are trying to execute is executed. Your comment about the not working insert query indicates this issue - cause old content is loaded instead of invoking the script, containing the query.

Halfpint Over a year ago

I'll most certainly add that to my toolbox - thanks for the advice :)

Halfpint Over a year ago

hmm very weird - after implementing the timestamp I am still getting an undefined index error Undefined index: values in D:\wamp\www\Kerr Pump - New\app\core\commands\update_results.php on line 5

dognose Over a year ago

@AlexSims that's because you are passing your values array with the parameter name query - therefore you have to access it using $_GET["query"].

|

Leo Zhuang · Accepted Answer · 2014-06-14 12:49:21Z

2

when Ajax is done, the success callback is triggered and the output of you php script is saved in data.

you can handle the data like this:

   $.ajax({
       type: "GET",
       url:  "./app/core/commands/update_results.php",
       data: { query : values },
       cache: false,
       dataType: "text",
       success: function(data) {
             document.write( data )
       }
   });

PHP, running at server, is unaware of what happening at the front-end browser and it simply respond to ajax request as any other normal http request. So the failure of SQL query has nothing to do with javascript, which only responsible for sending ajax request and receiving and handling the response. I guess there's some errors in your php script.

edited Jun 14, 2014 at 12:49

answered Jun 14, 2014 at 12:31

Leo Zhuang

4892 silver badges10 bronze badges

2 Comments

Halfpint Over a year ago

thanks Leo that makes sense. However, earlier I tried to run an INSERT query in the php script and nothing was sent to the db, would this also be caused by not writing a success callback?

Halfpint Over a year ago

Yep I think I found the problem, pretty sure its because I didnt check if variables were set - therefore it would just not process the script - thanks for your help

Collectives™ on Stack Overflow

PHP script not echoing data when called via AJAX

2 Answers 2

7 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

7 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related