Comparing Data Before and After Form Submission - php

Question

I have a form page in which many of the elements are saved to different tables and different rows in my db. In order to minimize db calls I would like to compare the data before and after form submission, then I can write a function which will only update data that has been changed. To accomplish this I am saving the array that I used to build the form in a session file:
$this->session->set_tempdata('form_values_'.$item['id'],json_encode($item), 86400);
On form submission I retrieve this data and compare it to the $_POST:
$pre_post = json_decode($_SESSION['form_values_'.$_POST['id']], true);
Everything works great except in a few textareas where there is a "." in my test data. For some reason these fields come back as not equal even though I'm not changing the data.
It is definitely the period that is causing the problem, when I remove it it works fine. On the other hand there are other textareas that have periods that are not causing problems.
I thought it might be codeigniter's XSS filtering, but I removed that and it made no difference.
Originally i was using serialize to encode the array for storage, but I switched to json_encode and again it made no difference.
Here is the code I am using to compare the values:
$pre_post = json_decode($_SESSION['form_values_'.$_POST['id']], true);
$post = $this->security->xss_clean($_POST);
foreach ($post as $key => $value) {
if( !isset($pre_post[$key]) || trim($value)!=trim($pre_post[$key]) ){
$post_post[$key] = $value;
}
}
Any ideas?

Answer 1

Try this code may be it help you
$select = "SELECT * FROM ".$table_name." WHERE ".$field_name ." = '".$value."'";
$result_latest = mysql_query($select) or trigger_error(mysql_error());
while($row = mysql_fetch_array($result_latest,MYSQL_ASSOC))
{
$data_new = array_intersect_key($row,$data);
foreach($data_new as $k=>$v)
{
if(strcmp($row[$k],$data[$k]) != 0)
{
$string .= '`'.$k.'` = "'.$data[$k].'" ,';
}
}
}
$string = rtrim($string, ",");
if($string != NULL){
$update_sql = "UPDATE ".$table_name." SET ".$string." WHERE ".$field_name." = "."'".$value."'";
$query = $CI->db->query($update_sql);
}