PHP Prepared Statements, how to shift data from one column to another - php

Question

I'm trying to move the data from one column in my table, to another, and then setting the initial column back to zero. While the initial column is reset back to zero, it also adds that zero onto the end of target column (I'll provide some screenshots for context).
Here is my code:
function complete_da($da_id) {
include 'connect.php';
include 'globals.php';
retrieve_user_data($_SESSION['logged_in']);
nation_data_grab($_SESSION['logged_in']);
echo "u_n_i: ".$user_nation_information['active_da']." <br>";
$ret_da_info_sql = "SELECT `active_da`, `completed_da` FROM `nations` WHERE `nations`.`user_id` = ?;";
$ret_da_info_stmt = mysqli_stmt_init($connect);
if(!mysqli_stmt_prepare($ret_da_info_stmt, $ret_da_info_sql)) {
echo "Statement 1 Failed";
} else {
mysqli_stmt_bind_param($ret_da_info_stmt, "i", $user_data['id']);
mysqli_stmt_execute($ret_da_info_stmt);
// Use get_result for *, bind_result for specific columns
mysqli_stmt_bind_result($ret_da_info_stmt, $active_da, $completed_da);
mysqli_stmt_fetch($ret_da_info_stmt);
echo "u_n_i: ".$user_nation_information['active_da']." <br>";
$updated_cda_str = ($completed_da .= ",".$active_da);
}
mysqli_stmt_close($ret_da_info_stmt);
$update_compl_with_active_sql = "UPDATE `nations` SET `completed_da` = ? WHERE `nations`.`user_id` = ?;";
$update_compl_with_active_stmt = mysqli_stmt_init($connect);
if(!mysqli_stmt_prepare($update_compl_with_active_stmt, $update_compl_with_active_sql)) {
echo "Statement 2 Failed";
} else {
mysqli_stmt_bind_param($update_compl_with_active_stmt, "si", $updated_cda_str, $user_data['id']);
mysqli_stmt_execute($update_compl_with_active_stmt);
$set_active_zero_sql = "UPDATE `nations` SET `active_da` = ? WHERE `nations`.`user_id` = ?;";
$set_active_zero_stmt = mysqli_stmt_init($connect);
$zero = 0;
if(!mysqli_stmt_prepare($set_active_zero_stmt, $set_active_zero_sql)) {
echo "Statement 2 Failed";
} else {
mysqli_stmt_bind_param($set_active_zero_stmt, "ii", $zero, $user_data['id']);
mysqli_stmt_execute($set_active_zero_stmt);
}
mysqli_stmt_close($set_active_zero_stmt);
}
mysqli_stmt_close($update_compl_with_active_stmt);
mysqli_close($connect);
}
Here is my table before the function is run:
Before
Table after function has run:
After
When run, the debugging echos I used to check to see if the 'active_da' is set correctly produces this result (the 4 is the button ID, they are just triggers for the function for now):
Results from echo
My question is, how can I just simply transfer the 'active_da' column onto the end of the 'completed_da' column without adding that extra zero?
EDIT: I believe this is the query that's throwing it off
$set_active_zero_sql = "UPDATE `nations` SET `active_da` = ? WHERE `nations`.`user_id` = ?;";
$set_active_zero_stmt = mysqli_stmt_init($connect);
$zero = 0;
if(!mysqli_stmt_prepare($set_active_zero_stmt, $set_active_zero_sql)) {
echo "Statement 2 Failed";
} else {
mysqli_stmt_bind_param($set_active_zero_stmt, "ii", $zero, $user_data['id']);
mysqli_stmt_execute($set_active_zero_stmt);
}