Tutorial: How to build a poll system with PHP and mySQL
6. What we need now is a way to test if there are questions or not in the poll. So now that we know we have a poll, we can begin showing its questions. So lets add some php code into our HTML. I prefer nesting PHP in html, as HTML nested in php can sometimes look very ugly. Both are ugly, but what can you do? So add the code below this line:
This:
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<table width="300" cellpadding="0" cellspacing="0" border="0" align="center">
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<tr>
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</tr>
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<?php
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$query = mysql_query("SELECT * FROM `questions` WHERE `pid`='".$poll['id']."' ORDER BY `question`");
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if($questions > 0){
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?>
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<tr>
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<td valign="top">
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<form name="poll" method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
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<table width="100%" cellpadding="0" cellspacing="0" border="0">
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<?php
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?>
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<tr>
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<td valign="top"><input type="radio" name="questions" value="<?php echo $question['id']; ?>" /></td>
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</tr>
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<?php
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}
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?>
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<tr>
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<td valign="top" colspan="2" align="center"><input type="submit" name="vote" value="Submit Vote" /></td>
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</tr>
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</table>
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</form>
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</td>
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</tr>
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<?php
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}
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?>
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</table>
Below this:
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if($rows > 0){
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$title = $poll['name'];
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} else {
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$title = 'No Poll Yet';
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}
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?>
Yep, big nesting of HTML and PHP. Time to explain it!
Firstly we make another query to the database. The purpose of this one is to find the questions of the poll. So it asks: Give me everything that has the id of the poll we are looking for. Remember how we selected the poll title above and got the name with $poll['name']? Well we are now using the $poll['id'] column. So what is happening is we are using the id of the poll, and matching it up to any matching records in the questions table. Thats right! A series of questions belong to a single poll, one to many relationship, A+.
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if($questions > 0){
We then get the number of rows and then test if the poll has any questions or not. If it doesnt then we skip the entire questions cycle and just close off the html. We then set up the HTML to display a form etc. This is not a html class. But next comes the questions cycle, where we use the response from the database.
This is a common way to run through an array. It executes row by row, until there are no more rows to display. All items from the array are accessible via the $question variable, much like we did above with the $poll variable. So through each look the code will display:
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<input type="radio" name="questions" value="<?php echo $question['id']; ?>" />
This prints out a radio button, with the $question id as each ones value, this is so we can later track what item was selected, and the question title itself.
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<input type="submit" name="vote" value="Submit Vote" />
A submit button is then displayed. If we didn't have our database setup the way it is, we might have to use a hidden field here, to display the poll id number in the form somewhere, but we will just be inserting the question id's into the database, as they are unique and an easy way to track! The loop and the number of rows test is then closed off and that is that for the interface for user input!
If this section has confused you, try to look at the PHP itself, ignore the HTML code. When programming always have the logic clear in your head, styling and design comes later. So if you don't follow how the selection is being tracked yet, don't worry, you will probably realise how in this next section.
17 Responses to “Tutorial: How to build a poll system with PHP and mySQL”
By Cristi
on Jun 11, 2008
It would be perfect if it had a form to add the question and a form to edit them. Anyway Good Job.
By VoiDeT
on Jun 11, 2008
Yep sure.
You should take the guestbook tutorial and build that feature yourself! It is not hard at all
By chor khee
on Jul 16, 2008
nice one man! just a simple question. Can this be done using jsp and mYsql? are there any links for that?
By VoiDeT
on Jul 16, 2008
Hey Chor Khee,
I don’t know JSP, sorry.
Have fun with the port!
By Ana
on Jul 25, 2008
Thank you very much it really is great, it gave me the whole picture. I am using Access data base, how can I use this nice piece of code for Access. Thanks again.
By Hunter
on Aug 11, 2008
Hi,
I downloaded the source, and uploaded it in tact, minus editing in my database information.
I get this error:
http://www.nineprinces.org/hunter/php/tutorials/
”
Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/backline/public_html/hunter/php/tutorials/poll.php on line 4″
What’s up w/ that?
By Hunter
on Aug 11, 2008
Nm, fixed it
By VoiDeT
on Aug 11, 2008
And how did you fix it?
By Hanayo
on Sep 24, 2008
I tried working on it but I as totally lost when it came to the whole phpmyAdmin thing??
I couldn’t figure out what you were talking about the click Insert or whatever since I didn’t see that anywhere on my page…
Like I know how to read html/css fairly well and can read xhtml. But php is what I’m learning, and so i know i put the codes in all the right spots but I don’t know what you meant by that and I tried but I dont’ think i got it…
http://www.aestheticloveinc.com/poll/index.php and it’s just blank….
By blckheart
on Sep 25, 2008
RE: And how did you fix it? Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in
To fix the error, you will have to connect to the database. In the downloaded files there is no config.php file or db.inc file to connect to the database, therefore the mysql_num_rows cannot find any info from the database, because there is no connection to the database. Or at least this is what happened in my case.
To connect to the database use the following code in the poll.php file or create a seperate config.php file and just use an include ‘config.php’; or require ‘config.php’; in the top of your poll.php file
//Connection to Database
$hostName = “localhost”;
$databaseName = “yourdatabasename”;
$databaseusername = “yourdbusername”;
$dbpassword = “yourdbpassword”;
$connect = @mysql_connect($host, $yourdbusername, $yourdbpassword);
if (!mysql_select_db($databaseName, $connect))
echo ‘Could not connect to database’;
I hope this helps, i dont know why someone would ask for help on the error and then say he fixed it without giving a solution, he has the time to ask but not the time to help, i think that sucks!
By VoiDeT
on Sep 27, 2008
blckheart what do you think is sitting in the root folder? would it be a config.php file by anychance? With this code in it?
< ?php
//database settings
$hostname = 'localhost';
$username = 'yourusername';
$password = 'yourpassword';
$dbname = 'poll';
$connect = mysql_connect($hostname, $username, $password);
mysql_select_db($dbname);
?>
Look at the files.
By BlueDevil18
on Sep 28, 2008
I set everyhing up. Added a New Poll and Questions to the poll with the correct pid. However, when I browse to the file(poll.php) on the server, it still comes up “No Poll Yet” Am I not doing something?
By BlueDevil18
on Sep 28, 2008
I need some help with this. I think i set up up correctly, but i still get “no poll yet”
By Rkrueger
on Oct 12, 2008
hey i was doing this and it came up with the error that the function “max()” doesn’t have enough parameters..
can someone check this out?
By Hodde
on Oct 28, 2008
I get the “no poll yet”-message too.. and i’m also pretty sure i set the poll up correctly..
By Stonedeft
on Dec 13, 2008
You should have separated codes and html. It gets real confusing I have to strip html tags the poll.php for me to review the code.
Well I got the idea but man you should recode this to for web 2.0 standards
By VoiDeT
on Dec 13, 2008
Thank you for the comment,
Maybe you could say something like, maybe you should use objects, or logic from design separation, but web 2.0 standards haha
Web 2.0 standards in php LOL