Update db tables of only updated fields of form- JQuery, PhP - php

Question

I have a huge multistep form with data for multiple tables in mysql db. For every field my html is like-
input type="text" name="names" value="" // value set using php echo
On submit at php I am doing this for all the fields of my form-
$name=$_POST['names'] ?? ' '
to avoid unidentified index and unidentified variable
Then i update my first table and write log that its updated.
$query=mysqli_query($con,"UPDATE teacherpersonal set name='$name' ... where id=$id");
write_mysql_log("teacherpersonal updated", "facultydetails", $id).
I have defined write_mysql_log.
And similarly i update all the remaining tables with either the updated values or blank ("") values.
Since you can see that update query always executes even if the fields are not changed. Hence it is always logged that the tables are updated. But that's not what I want. I want to update only those fields in the table which are changed and remaining stay intact and log only those tables which are thus updated. Many tables won't be updated this way as the user might change only few details.
Using jquery and php.
My write_mysql_log is
function write_mysql_log($message, $db, $faculty_id)
{
$con=mysqli_connect("localhost","root","");
mysqli_select_db($con,"facultydetails");
// Construct query
$sql = "INSERT INTO my_log (message, faculty_id) VALUES('$message', '$faculty_id')";
$query=mysqli_query($con, $sql);
// Execute query and save data
if($query) {
echo 'written to the database';
}
else {
echo 'Unable to write to the database';
}
}

Answer 1

This you can achieve in 2 different ways.
1) With the help of jQuery check the values which are updated, post only those values to the php script
2)At the time of updating the check the current values with the updated one based on that criteria update the db tables.
solution 1 is less time taking process compare to the other.

Answer 2

You need to update only the user edited value, by doing this you can achieve it;
$oldvalue = array("username" => "green", "email" => "green#mail.com","dob" => "111");
$newvalue = array( "email" => "green#mail.com","dob" => "111","username" => "blue");
$updates = array_diff($newvalue, $oldvalue);
$implodeArray = implode(', ', $updates);
$sql = ("UPDATE user WHERE userID=$userID SET $implodeArray");
mysql_query($sql,$this->_db) or die(mysql_error());
mysql_close();
Output:
$updates = array_diff($newvalue, $oldvalue);
will have:
Array ( [username] => blue )
which is changed one

Answer 3

Ok after considering many options like-
create json object for old and new data and then compare and check which values changed and update that table and log it.
Or create a php array with old and new data and check diff then do the same (as suggested by Ram Karuppaiah)
Or a bad idea to have a flag on every input and then mark which ones have changed using onkeyup jquery event then try to update only those fields tables.
So finally what i did is that i let the form get submitted with all the data. As earlier i am taking the data in php as $name=$_POST['names'] ?? ' ' (blank if nothing is submitted or if something submitted then its value).
Before update statement in php, i am querying the table and comparing the database values with the values i got, if all same i dont do anything. If not then i update the table with the new values and log the change.