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Basic Poll Script in PHP

Author: Adman More by this author

Added: Apr 20, 2005 Rating:

Level: Professional Software: PHP Editors

This article will teach you how to write a basic poll script in php. You will mysql and a new version of PHP.

The first step is to create a database that will hold the information all the polls we want. For this article we will be creating a poll that will have 3 options. Yes, No, and Not Sure. So we will want to create feilds for each of those. I used Option1, Option2, and Option. We will also need a title and a question to ask. I created those as varchars. Another feild will hold the total number of votes total. The most important colum is the ID colum which will be an auto increment tinyint that will help use to select, edit, and add new records. Here is the schema of my table:

# Table structure for table `poll_data`
#

CREATE TABLE poll_data (
  ID tinyint(4) NOT NULL auto_increment,
  Option1 tinyint(4) NOT NULL default '0',
  Option2 tinyint(4) NOT NULL default '0',
  Option3 tinyint(4) NOT NULL default '0',
  Votes tinyint(4) NOT NULL default '0',
  Title varchar(25) NOT NULL default '',
  Question varchar(50) NOT NULL default '',
  PRIMARY KEY  (ID)
) TYPE=MyISAM;

Now that we have the table set up, we want to get coding. Most of the time, when you are going to write a script or program you will want to break it down into small parts. Like:

Display the Title and Question of the Poll.
Show the captions of each vote option, the percent of the total votes, and the total votes for each.
Create a file that will allow the user to vote in the poll.

Those are the main functions of our script. Now that we those set up, we want to break each of those down into smaller objectives.

Display the Title and Question of the Poll
a. Connect to the database
b. Select the Newest record from the database
Show Captions of each vote.
a. Select the votes for each option, and select the total votes in the poll.
b. Take the number of votes and divide by the total number of votes to find the percent.
Create a file that will allow the user to vote in the poll
a. Update the row where the user voted.

We will want to set up some variables to help us connect to the database. Like This:

$dbhost = "localhost";
$dbname = "YourDataBase";
$dbuser = "YourUserName";
$dbpass = "YourPass";

Then, we will connec to the database.

$link_id = mysql_connect($dbhost, $dbuser, $dbpass);
mysql_select_db($dbname);

Now we have some queries to do. One to select the current Title and Quesiton of the Poll, and the other to get all the information on the votes and total votes. There is a problem though. We need to get information about the current or newest poll. This is where are ID colum comes into play. We can select the Title and Question in Descending Order so that the newest record will be at the top. See, every time a new row is inserted, the ID colum has 1 added to it, or it is Auto Incremented. So, the newest row will have the largest ID, so we can sort that form Largest to Smallest to get the newest record. Also, we only want one row to be returned so we tack on Limit 1 at the end. Then we want to turn that result into an array for easy access.

$sql = "SELECT `Title`,`Question`,`ID` FROM `poll_data` ORDER BY `ID` DESC LIMIT 1"; if(!($result = mysql_query($sql))) die(mysql_error()); $PollData = mysql_fetch_array($result)

Now that we have the Title and Question of the poll, we want the all the good stuff, the votes and the percentages. Again we want the newest record, so we use desc order again.

$sql = "SELECT `Option1`,`Option2`,`Option3`,`Votes` FROM `poll_data` WHERE `ID` = '" . $PollData['ID'] . "' ORDER BY `ID` DESC LIMIT 1";
if(!($result = mysql_query($sql))) die(mysql_error());
if(!($VoteData = mysql_fetch_array($result))) die(mysql_error());

Now for some math. We need to find out the percentages that each choice has. Once we find that percent, we can make an image and set it to have a width of that percentage. The image will give us the bars, that we all love. To find the percent we need to get the votes that a choice has then divide it by the total votes in the poll, then multiply it by 100, then round that number to get a 2 digit number. After all the math is done, we add a % sign to the end of it. What is there are no votes for a certain option? We will get an unsightly error saying divison by 0. So we Check to see if the votes are 0 and if they are, set the percent to 0%.

if($VoteData["Option1"] != 0) {
$VotePercent1 = Round(($VoteData["Option1"] / $VoteData["Votes"]) * 100) . "%";
} else {
$VotePercent1 = 0 ."%";
}
if($VoteData["Option2"] != 0) {
$VotePercent2 = Round(($VoteData["Option2"] / $VoteData["Votes"]) * 100) . "%";
} else {
$VotePercent2 = 0 ."%";
}
if($VoteData["Option3"] != 0) {
$VotePercent3 = Round(($VoteData["Option3"] / $VoteData["Votes"]) * 100) . "%";
} else {
$VotePercent3 = 0 ."%";
}

Now that we have all the data we need, we need to display that information in the table. Before you do this, you need to make an image that is 20 pixels high and 1 pixel wide of any color. This part is very self explainatory. We have a table and output the data. We set the image width to be the vote percent. We have a form with radio buttons to let the user pic their vote.

<html>

<head>>
<title>Basic Poll - Written by Adman</title>
</head>
<body>
<form method="POST" action="vote.php">
<table width="500" border="1" cellspacing="0" cellpadding="8">
<tr>

<td colspan="3"><b><?=$PollData['Title']?> - <?=$PollData['Question']?></b></td>
</tr>
<tr>
<td width="35%">

<input type="radio" name="Vote" value="Option1">
Yes</td>
<td width=60%>
<img src="/img_articles/4349/bar.gif" width="<?=$VotePercent1?>" height="20">
</td>

<td><?=$VoteData["Option1"]?> Votes</td>
</tr>
<tr>
<td width="35%">
<input type="radio" name="Vote" value="Option2">

No </td>
<td width=60%>
<img src="/img_articles/4349/bar.gif" width="<?=$VotePercent2?>" height="20">
</td>
<td><?=$VoteData["Option2"]?> Votes</td>

</tr>
<tr>
<td width="35%">
<input type="radio" name="Vote" value="Option3" >
Not Sure</td>
<td width="60%">

<img src="/img_articles/4349/bar.gif" width="<?=$VotePercent3?>" height="20">
</td>
<td><?=$VoteData["Option3"]?> Votes</td>
</tr>

<tr>
<td colspan="3">
<center>
<input type="submit" name="Submit" value="Vote">
</center>
</td>

</tr>
</table>
</form>
</body>
</html>

Now that we have the display done. We are ready to write the script that lets the user vote in the poll. On to the next page! First we check to see the user actually did vote, if not, exit the script. Since the variable was passed through a post form, we have to use $_POST.

if(empty($_POST["Vote"])) 
    die("You did not enter your vote");

If the script is still running, we need to connect to the database like we did before, and select the current data on the poll. We want to select all the vote data form the newest record. Then turn it into an array.

$dbhost = "localhost";
$dbname = "misc";
$dbuser = "root";
$dbpass = "trigger";

$link_id = mysql_connect($dbhost, $dbuser, $dbpass);
mysql_select_db($dbname);

$sql = "SELECT `Option1`,`Option2`,`Option3`,`Votes`,`ID` FROM `poll_data` ORDER BY `ID` DESC LIMIT 1";
if(!($result = mysql_query($sql))) die(mysql_error());
if(!($PollData = mysql_fetch_array($result))) die(mysql_error());

Now that we have a database connection, we need to decided which option to update. We need to add 1 to the current number of votes, and add 1 to the total number of votes. After that has been done, we need to update that row in the database. So we use the update clause to set the new records. Just like before we need to user $_POST becuase the variables we transmitted through a post metod form.

if($_POST["Vote"] == "Option1") {
$Votes1 = $PollData["Option1"] + 1;
$TotalVotes = $PollData["Votes"]+ 1;

$sql = "UPDATE `poll_data` SET `Option1`='$Votes1', `Votes`='$TotalVotes' WHERE `ID` = '". $PollData['ID'] . "' LIMIT 1";
if(!($result = mysql_query($sql))) die(mysql_error());
echo "Vote successful! <a href=\"index.php\">Back</a> to the poll.";
}
else if ($_POST["Vote"] == "Option2"){
$Votes2 = $PollData["Option2"] + 1;
$TotalVotes = $PollData["Votes"]+ 1;

$sql = "UPDATE `poll_data` SET `Option2`='$Votes2', `Votes`='$TotalVotes' WHERE `ID` = '". $PollData['ID'] . "' LIMIT 1";
if(!($result = mysql_query($sql))) die(mysql_error());
echo "Vote successful! <a href=\"index.php\">Back</a> to the poll.";
}
else {
$Votes3 = $PollData["Option3"] + 1;
$TotalVotes = $PollData["Votes"] + 1;

$sql = $sql = "UPDATE `poll_data` SET `Option3`='$Votes3', `Votes`= '$TotalVotes' WHERE `ID` = '". $PollData['ID'] . "' LIMIT 1";
if(!($result = mysql_query($sql))) die(mysql_error());
echo "Vote successful! <a href=\"index.php\">Back</a> to the poll.";
}

voilla!! Your done. All you have to do is save the file. Those are the basics of a poll. In my next article, I will tell you how to administer your poll. If you have any problems, talk to me on TutorialForums, my email is z-team@attbi.com. Feel free to email me to talk me, I will be glad to help you.

Author's URL: Adman