PHP, AJAX: large data being truncated - php

Question

The Problem
I'm using jQuery to post a (relatively) large amount of data to a web system I am migrating from Ubuntu to CentOS (a painful process). The problem is that the data being received is truncated. Sending the same data from the server to the client results in no truncation.
The amount of data being 'sent' (that is, what I'm seeing while debugging Javascript) is 116,902 bytes (the correct amount of data), whereas the amount of data being received is approximately 115,668 bytes: this number seems to vary, making me believe the problem may be time related. The transaction completes (receive, response) in approximately 3.1 seconds, not a huge amount of time. Are there any settings I should examine?
That idea aside, my PHP installation is configured to accept 8M of post data and use to 128M of physical memory, which seems plenty enough.
The jQuery code is below. I'm quite sure this isn't the problem, but I've included it as requested.
Receiving:
function synchronise_down()
{
$.ajax({url: "scripts/get_data.php",
context: document.body,
dataType: "json",
type: "POST",
success: function(result)
{
// Fix the state up.
update_data(result);
// Execute on syncronise.
execute_on_synchronise();
},
error: function(what, huh)
{
IS_WAITING = false;
}
});
}
Sending:
function synchronise_up()
{
var serialised = MIRM_MODEL.serialise();
LAST_SERIALISED = new Date().getTime();
$.ajax({url: "scripts/save_model.php",
context: document.body,
dataType: "json",
data: {"model":serialised},
type: "POST",
success: function(result)
{
// Fix the state up.
update_data(result, true);
// Execute on syncronise.
execute_on_synchronise();
},
error: function(what, huh)
{
IS_WAITING = false;
}
});
}
Workaround (Wouldn't call this a solution)
Edit: I've 'fixed' this, but not necessarily found out what the problem is and how to solve it. It's an interesting problem so I'll describe my workaround and leave the question open.
What I'm doing is rather than letting jquery handle the serialisation of my large data, I'm doing it myself first, essentially serialising twice. the code for this is as follows:
function synchronise_up()
{
var serialised = JSON.stringify(MIRM_MODEL.serialise());
LAST_SERIALISED = new Date().getTime();
$.ajax({url: "scripts/save_model.php",
context: document.body,
dataType: "json",
data: {"model":serialised},
type: "POST",
success: function(result)
{
// Fix the state up.
update_data(result, true);
// Execute on syncronise.
execute_on_synchronise();
},
error: function(what, huh)
{
IS_WAITING = false;
}
});
}
The important line is of course:
var serialised = JSON.stringify(MIRM_MODEL.serialise());
Now, when it hits the server, I need to decode this data because it's been serialised twice. There are added costs with this 'solution': sending more data, doing more work. The question still remains: what's the problem, and what's the real solution?

Answer 1

Check the following php.ini variables:
post_max_size
max_input_vars - This might actually be the culprit because it truncates data

Answer 2

Try setting jQuery's ajax timeout parameter to a high number (note, it's in milliseconds, so you'll probably want 10000 which is 10 seconds).
Some other options to try:
1. Check that your PHP max execution time is a decent amount. I doubt this would be related but it's possible.
2. On jQuery's error function, run console.log(xhr) on the XHR result (you'd have to do this in Chrome or find another method of seeing the result). XHR is an XHR object that contains debug information on what happened with the connection e.g. Status codes, timeout info, etc.
EDIT: Also, have you checked the max size of the field in your Database? It's quite possible that the Database is automatically truncating the information.

Answer 3

my gut feeling is that it's a php timeout related, i've never heard of a javascript timeout - and I have jquery's running for 3 or 4 hours, but then they continue to post little updates (like a _SESSION progress bar in PHP ... but I digress.. anyway you HAVE to use firefox for this, IE doesn't "believe" you when you know what you are doing and times out after about 40 minutes) ~ chrome wasn't used by me at the time.
Actually, come to think of it, you say you are migrating to CentOS sounds to me like is HAS to be server related. You are simply looking in the wrong place.
BTW congrats on CentOS it's AMAZING! I would do it the easy way and have an entire LAMP CentOS VM just fo rthis app (try not to faff with the vhosts for this it's v v messy) and simply set the whole apache/php install to be insanely high.
The correct php.ini settings are
max_input_time //(not max_execution_time!)
upload_max_filesize
post_max_size
// .. and try
memory_limit

Answer 4

PHP POST/GET/COOKIE are limited to 1000 entries by default. Everything above that is ignored. It is the number of entries that count, not the actual amount of data.
I sugest you to edit your php.ini and set the max_input_vars setting to a greater value.
Regards.