buy.php - shared from CS50 IDE

buy.php

<?php

    // configuration
    require("../includes/config.php");
    
    $number = isset($_POST["number"]) ? $_POST["number"] : 0;
    $symbol = isset($_POST["symbol"]) ? $_POST["symbol"] : "";
    $spent = lookup($symbol)["price"] * $number;
    $cash = CS50::query("SELECT cash FROM users WHERE id = ?", $_SESSION["id"]);
    $_owned = CS50::query("SELECT shares FROM Stocks WHERE user_id = ? AND symbol = ?", $_SESSION["id"], $symbol);
    $owned = isset($_owned[0]["shares"]) ? $_owned[0]["shares"] : 0;
    $new_cash = $cash[0]["cash"] - $spent;
    $new_shares = $owned + $number;

    // if user reached page via GET (as by clicking a link or via redirect)
    if ($_SERVER["REQUEST_METHOD"] == "GET")
    {
        // else render form
        render("/../views/buy_form.php", ["title" => "Bought"]);
    }

    // else if user reached page via POST (as by submitting a form via POST)
    else if ($_SERVER["REQUEST_METHOD"] == "POST" && lookup($symbol) != false && $number != false)
    {
        // check valid number entered
        if (preg_match("/^\d+$/", $_POST["number"]) != true)
        {
            apologize("Please enter a positive integer.");
        }

        // check user has enough cash
        if ($spent > $cash[0]["cash"])
        {
            apologize("You do not have enough cash.");
        }
        
        // edit the database
        $temp = CS50::query("INSERT INTO Stocks (user_id, symbol, shares) VALUES(?, ?, ?) ON DUPLICATE KEY UPDATE shares = ?", $_SESSION["id"], $symbol, $number, $new_shares);
        $_temp = CS50::query("UPDATE users SET cash = ? WHERE id = ?", $new_cash, $_SESSION["id"]);
        
        render("/../views/buy_template.php", ["number" => $number, "symbol" => $symbol, "spent" => $spent]);
    }
    
    else if ($_SERVER["REQUEST_METHOD"] == "POST")
    {
        apologize("Invalid entry.");
    }

?>