Converting a whole number to decimal value in php

Question

I have a PHP application that is supposed to insert an monetary value into a MariaDB whose table column was set to decimal (10,2)

To ensure the formatting is correct I initially did an echo statement to make sure the result using what I thought should be the correct formatting....

number_format($variable-to-be-converted, 2, '.', '');

However, when I assign that format conversion I get told (by the mysqli error code) that the decimal value is incorrect. I have tried adjusting the decimal placing between 13, 10, and 4; alas no joy.

Any ideas would be appreciated t-i-a

include '../includes/dbt.php';
    
//make sure a residence tile was selected or send them back to /play/index.php
if (!isset($_GET['residence'])) {
    //code here
} else if (isset($_COOKIE['startingBal'])){
    session_start();
    setCookie("residence", $_GET['residence'], time() + 86400);
    $residence = $_COOKIE['residence'];
                
    $balance    = $_COOKIE['startingBal'];
    $newBal     = '';
                
    switch ($residence) {
    case 'option1':
        $newBal = $balance - 3200;
        break;                          
    case 'option2':
        $newBal = $balance - 3000;
        break;                          
    case 'option3':
        $newBal = $balance - 800;
        break;
    case 'option4':
        $newBal = $balance - 700;
        break;                          
    default:
        $balance;
    }
    $formattedNewBal    = number_format($newBal, '2','.','');
    $ingameStatsUpdate  =  "INSERT INTO ingameStats (`nickname`, `residence`, `newBal`) VALUES ('$nickname', '$residence', '$formattedNewBal')";
            
    if (mysqli_query($conn, $ingameStatsUpdate)) {
                
        echo "New record created successfully";
    } else {
        echo "Error: " . $sql . "<br>" . mysqli_error($conn);
    }
        
    //unset starting balance cookie since now the database will keep track of the balance moving forward
    setCookie("startingBal", "", time() -3600);
                    
    // close connection 
    mysqli_close($conn);
}
    

Answer 1

There's two problems.

First, you're not setting $residence correctly. Calling setcookie() doesn't update the $_COOKIE array, so $residence = $_COOKIE['residence']; won't set it to the value you just assigned. See Why are my cookies not setting?

Second, your default: case doesn't set $newBal. So if none of the cases match, $newBal still has an empty string, which is an invalid floating point value in MySQL.

    session_start();
    $residence = $_GET['residence'];
    setCookie("residence", $residence, time() + 86400);
                
    $balance    = $_COOKIE['startingBal'];
                
    switch ($residence) {
    case 'option1':
        $newBal = $balance - 3200;
        break;                          
    case 'option2':
        $newBal = $balance - 3000;
        break;                          
    case 'option3':
        $newBal = $balance - 800;
        break;
    case 'option4':
        $newBal = $balance - 700;
        break;                          
    default:
        $newBal = $balance;
    }