PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

500 Chapter 22 Generating Images
In this example, you run a poll on your website to test whom users will vote for in a
fictitious election.You store the results of the poll in a MySQL database and draw a bar
chart of the results using the image functions.
Graphing is the other thing these functions are primarily used for.You can chart any
data you want—sales, web hits, or whatever takes your fancy.
For this example, we spent a few minutes setting up a MySQL database called poll.
It contains one table called poll_results, which holds the candidates’ names in the
candidate column and the number of votes they received in the num_votes column.
We also created a user for this database called poll, with password poll.This table is
straightforward to set up, and you can create it by running the SQL script shown in
Listing 22.3.You can do this piping the script through a root login using
mysql -u root -p < pollsetup.sql
Of course, you could also use the login of any user with the appropriate MySQL
privileges.
Listing 22.3
pollsetup.sql—Sets Up the Poll Database
create database poll;
use poll;
create table poll_results (
candidate varchar(30),
num_votes int
);
insert into poll_results values
(‘John Smith’, 0),
(‘Mary Jones’, 0),
(‘Fred Bloggs’, 0)
;
grant all privileges
on poll.*
to poll@localhost
identified by ‘poll’;
This database contains three candidates.You provide a voting interface via a page called
vote.html.The code for this page is shown in Listing 22.4.
Listing 22.4 vote.html—Allows Users to Cast Their Votes Here
Polling
Pop Poll
Who will you vote for in the election?
John Smith