在循环外面的未定义变量 - PHP

Question

I was wondering why I got an error saying Notice: Undefined variable: query_add_landdev_temp_payroll in C:\xampp\htdocs\op\ajax\ajaxLanddevNTPPayroll.php on line xx. for the past 2 weeks, it works perfect. When I tried to execute the code today, I got that kind of error. Here is my code:

$query_get_payroll = mysqli_query($new_conn, "SELECT ntp_with_ob_payroll_transaction.ntp_id, ntp_with_ob_payroll_transaction.allotment_code, ntp_with_ob_payroll_transaction.category_name, ntp_with_ob_payroll_transaction.block_number, ntp_with_ob_payroll_transaction.activity, ntp_with_ob_payroll_transaction.lot_number, ntp_with_ob_payroll_transaction.labor_cost, other_budget.quantity FROM ntp_with_ob_payroll_transaction JOIN other_budget ON ntp_with_ob_payroll_transaction.ob_id = other_budget.ob_id WHERE other_budget.transaction_id = $transaction_id AND other_budget.ob_number = '$ntp_number' AND is_payroll = 0");

while($row = mysqli_fetch_assoc($query_get_payroll)) {

    $ntp_id = $row['ntp_id'];
    $allotment_code = $row['allotment_code'];
    $category_name = $row['category_name'];
    $block_number = $row['block_number'];
    $activity = $row['activity'];
    $lot_number = $row['lot_number'];
    $labor_cost = $row['labor_cost']; //this is equivalent to unit cost
    $quantity = $row['quantity']; //this is equivalent to total percentage


    $query_add_landdev_temp_payroll = mysqli_query($new_conn, "INSERT INTO temp_payroll_landdev(ntp_id, userid, transaction_id, ntp_number, contractor_name, allotment_code, category_name, block_number, activity, lot_numbers, regular_labor, quantity) VALUES($ntp_id, $_SESSION[userid], $transaction_id, '$ntp_number', '$fullname', '$allotment_code', '$category_name', $block_number, '$activity', '$lot_number', '$labor_cost', '$quantity')");
}

if($query_add_landdev_temp_payroll) {

    echo 1;

    //database file name
    $database_file = $database.'.sql';
    $new_database_file = $new_database.'.sql';

    if(file_exists('backup/'.$new_database_file)) {

        unlink('backup/'.$new_database_file);

        //backup project database
        $command = "C:/xampp/mysql/bin/mysqldump --host=$new_host --user=$new_user --password=$new_pass $new_database > backup/$new_database_file";
        system($command);

    } else {

        //backup project database
        $command = "C:/xampp/mysql/bin/mysqldump --host=$new_host --user=$new_user --password=$new_pass $new_database > backup/$new_database_file";
        system($command);
    }
} else {

    echo 0;
}

Answer 1

If the query doesn't return any rows, mysqli_fetch_assoc() will return false the first time, so you'll never go into the loop, and never assign to the variable. If you then try to use the variable you get that warning.

You can give it a default initial value before the loop, or you can change your test to:

if (!empty($query_add_landdev_temp_payroll))

BTW, the variable only contains the result of the INSERT in the last iteration of the loop. Maybe you should put the if block inside the loop, right after the INSERT?

Also, there's no need to do INSERT in a loop. You can do the whole thing with a single query:

INSERT INTO temp_payroll_landdev(ntp_id, userid, transaction_id, ntp_number, contractor_name, allotment_code, category_name, block_number, activity, lot_numbers, regular_labor, quantity)
SELECT ntp_with_ob_payroll_transaction.ntp_id, ntp_with_ob_payroll_transaction.allotment_code, ntp_with_ob_payroll_transaction.category_name, ntp_with_ob_payroll_transaction.block_number, ntp_with_ob_payroll_transaction.activity, ntp_with_ob_payroll_transaction.lot_number, ntp_with_ob_payroll_transaction.labor_cost, other_budget.quantity 
FROM ntp_with_ob_payroll_transaction 
JOIN other_budget ON ntp_with_ob_payroll_transaction.ob_id = other_budget.ob_id 
WHERE other_budget.transaction_id = $transaction_id AND other_budget.ob_number = '$ntp_number' AND is_payroll = 0