One of the simplest and most popular add-ons to a Web site is anonline poll, allowing visitors to vote on hot-button issues. In thisarticle, find out how PHP can be used to build a powerful, good-lookingonline poll for your Web site, and also learn a little bit about its imageand cookie manipulation functions.
Once the database has been updated with the vote, it's a good idea to display the current results of the poll. This involves connecting to the database, using the $id variable to extract the correct record, calculate the total number of votes, and the percentage each option has of the total, and displaying this information in a table.
Here's what all that looks like in PHP:
// query successful,display status message...
echo "Thank you for voting. Here are the results so far:<p>";
// ...and tabulated results
// get a complete count of votes in each category
$query = "SELECT question, response1, response2, response3, votes1,
votes2, votes3, date from $table WHERE id = $id";
$result = mysql_db_query($database, $query, $connection) or die ("Could
not execute query: $query. " . mysql_error());
// assign the returned values to variables
list($question, $response1, $response2, $response3, $votes1, $votes2,
$votes3, $date) = mysql_fetch_row($result);
// count the total votes
$total = $votes1 + $votes2 + $votes3;
// calculate each as a percentage of the total, round to two decimals
$perc_votes1 = round(($votes1/$total)*100,2);
$perc_votes2 = round(($votes2/$total)*100,2);
$perc_votes3 = round(($votes3/$total)*100,2);
// print it all in a neat table
echo "<table border=0 cellspacing=0 cellpadding=5>";
echo "<tr><td colspan=3><b>$question</b></td></tr>";
// also display an image graph - more on this later!
echo "<tr><td>$response1</td><td> $votes1 ($perc_votes1%)</td><td
echo "<tr><td>$response2</td><td> $votes2 ($perc_votes2%)</td></tr>";
echo "<tr><td>$response3</td><td> $votes3 ($perc_votes3%)</td></tr>";
echo "<tr><td><font size=-2>Posted on " . fixDate($date) .
"</font></td><td><font size=-2>$total total votes</font></td></tr>";
// or error in query - display error message
echo "<i>Error! Please <a href=start.php>try again</a></i>";
You need to be careful when converting the absolute
numbers into percentages - if there aren't any votes yet, you can get some pretty strange "division by zero" errors. This error is not likely at this stage - after all, you've just added a vote - but it can crop up at a later stage. As we progress, you'll see the correction I've used to account for this situation.
The code snippet above references an image named "graph.php". If you're familiar with PHP's image generation function, you'll immediately divine that this is the PHP script used to dynamically generate the bar graph. I'll be discussing this a little later, so ignore it for the moment.
Finally, you'll see a reference to a fixDate() function in the last line of the table. This is a very simple function I wrote to convert the default MySQL date format into something a little more readable. Here's the function:
// format the date so that it looks prettier
$dateArray = explode("-", $val);
$val = date("j M Y", mktime(0,0,0, $dateArray, $dateArray,
Feed fixDate() a date in the default MySQL format (say,
"2001-03-07") and it will return something much friendlier ("7 Mar 2001").
And here's what the final result page looks like:
This article copyright Melonfire 2001. All rights reserved.