pset7 (buy): trouble comparing value of transaction with cash

Question

For some reason it is impossible for me to compare the cost of the buy-transaction with the user's cash balance in pset7. $value correctly comes up as a float, but $cash comes up as a string (even though it's defined as a decimal in my database), so I cannot compare them correctly. I tried casting $cash to a float, but that didn't help either. If someone could help me figure out why this is happenning, and how I can remedy this bug, I would massively appreciate it. My code is below:

<?php

// configuration
require("../includes/config.php");

if($_SERVER["REQUEST_METHOD"] == "GET")
{
    render("buy_form.php", ["title" => "Buy"]);
}
else if($_SERVER["REQUEST_METHOD"] == "POST")
{
    // error-checking #1
    if(empty($_POST["symbol"]) || empty($_POST["shares"]))
    {
        apologize("You need to input a symbol and quantity of shares.");
    }
    // check that shares is a whole positive number
    else if(preg_match("/^\d+$/", $_POST["shares"]) != TRUE || !is_numeric($_POST["shares"]))
    {
        apologize("You need to input a non-negative, numeric number of shares.");    
    }

    // get number of shares and the stock
    $stock = lookup($_POST["symbol"]);
    if($stock == false)
    {
        apologize("Stock not found.");
    }

    // calculate value of transaction
    $value = $stock["price"] * $_POST["shares"];

    //ensure that user can afford transaction
    $cash = CS50::query("SELECT cash FROM users WHERE id = ?", $_SESSION["id"]);
    var_dump($value, $cash);

    // insert stocks into user's portfolio
    // update user's cash
}

?>

Answer 1

If you take a look at this answer you will see that query() returns an array. So what you have to do is something like this:

$row= CS50::query("SELECT cash FROM users WHERE id = ?", $_SESSION["id"]);
$cash = $row[0]["cash"];