gistfile1.php

    /**
     * Returns a stock by symbol (case-insensitively) else false if not found.
     */
    function lookup($symbol)
    {
        // reject symbols that start with ^
        if (preg_match("/^\^/", $symbol))
        {
            return false;
        }

        // reject symbols that contain commas
        if (preg_match("/,/", $symbol))
        {
            return false;
        }

        // headers for proxy servers
        $headers = [
            "Accept" => "*/*",
            "Connection" => "Keep-Alive",
            "User-Agent" => sprintf("curl/%s", curl_version()["version"])
        ];

        // open connection to Yahoo
        $context = stream_context_create([
            "http" => [
                "header" => implode(array_map(function($value, $key) { return sprintf("%s: %s\r\n", $key, $value); }, $headers, array_keys($headers))),
                "method" => "GET"
            ]
        ]);
        $handle = @fopen("http://download.finance.yahoo.com/d/quotes.csv?f=snl1&s=$symbol", "r", false, $context);
        if ($handle === false)
        {
            // trigger (big, orange) error
            trigger_error("Could not connect to Yahoo!", E_USER_ERROR);
            exit;
        }

        // download first line of CSV file
        $data = fgetcsv($handle);
        if ($data === false || count($data) == 1)
        {
            return false;
        }

        // close connection to Yahoo
        fclose($handle);

        // ensure symbol was found
        if ($data[2] === "0.00")
        {
            return false;
        }

        // return stock as an associative array
        return [
            "symbol" => $data[0],
            "name" => $data[1],
            "price" => $data[2],
        ];
    }