Problems with Conditional..

lvollmer

I am trying to write a script that queries a database to find a userid and id category. If ANY results are found, then the user should not be allowed to continue. If no results are found, then the user should be allowed to vote on a category.

This script below is always returning "You already voted", even if the user has not voted before. The variables work, as I have tested them in the echo statements.

Any ideas?

<?php

$query = "select * from items where id_user= '$userid' and id_category =".$_GET["id"];
$result = mysql_query($query);

$rs=$rs_query=mysql_query($query);
$rs=mysql_fetch_array($rs_query);

if (($rs = 0))

{
echo "Go ahead and vote <br>";
echo $userid;
//testing variable

echo "<br>";
echo $GET["id"];
}
else
while(!($rs=0))
{
echo "You already voted<br>";
echo $userid;
//testing variable

echo "<br>";
echo $GET["id"];
exit();
}
?>

devinemke

$result = mysql_query("SELECT * FROM items WHERE id_user = '$userid' AND id_category = " . $_GET['id']) or exit(mysql_error()); 
if (mysql_num_rows($result)) 
{
	echo 'You already voted';
}
else
{ 
	echo 'Go ahead and vote'; 
}

Rodney_H_

Something to keep in mind for future reference is the different types of operators. You used someting similar to the following in your script:

[INDENT]if (($rs = 0)){
// do something
}[/INDENT]

You are using an assignment operator "=" edit. So, you need to use the Comparison Operator "==" to test for equality.

[INDENT]if ($rs == 0){
// do something
}[/INDENT]

lvollmer

I tried that chunk of code, and now it allows the user to vote even if they have already voted.

lvollmer

Thanks Rodney,
I had originally tried that and was still failing. I appreciate the info though.

Rodney H. wrote:
Something to keep in mind for future reference is the different types of operators. You used someting similar to the following in your script:

[INDENT]if (($rs = 0)){
// do something
}[/INDENT]

You are using an assignment operator "=", but assignment I think will always be true. So, you need to use the Comparison Operator "==" to test for equality.

[INDENT]if ($rs == 0){
// do something
}[/INDENT]

Not saying this to negate what Devinemke said, but for future reference. I have been an educator for twenty years, and I guess it is in my blood to make little references like this. :-)

Rodney_H_

lvollmer wrote:
Thanks Rodney,
I had originally tried that and was still failing. I appreciate the info though.

I wasn't saying to use it in THIS context, but in general.... Thought I made that clear... shrug

thorpe

how are you determining who has voted?

If ANY results are found, then the user should not be allowed to continue

based on that comment devinemke's code works.

lvollmer

thorpe wrote:
how are you determining who has voted?

based on that comment devinemke's code works.

The code doesn't work, it allows the user to vote even if they have previously voted.

<?
@session_start();
require_once("engine.php");

// Checks if the user is authorized
if (!is_authorized())
{
print "You must login before voting!";
exit();
}

// Checks the item input
if (!check_item_id(@$_GET["id"]))
{
print "Incorrect item id or missing";
exit();
}
?>
<?php
// Pick up the user ID of the user
$link = mysql_connect("localhost", "user", "pass") OR DIE("Unable to connect to the database");
mysql_select_db("bestof");

$query = "select * FROM users where username= '".$_SESSION["username"]."'";
$result = mysql_query($query);

$rs=$rs_query=mysql_query(($query),$link);
$rs=mysql_fetch_array($rs_query);

$userid = $rs['id'];
//echo $userid
?>

DevinMikes code
<?
$result = mysql_query("SELECT * FROM items WHERE id_user = '$userid' AND id_category = " . $_GET['id']) or exit(mysql_error());

if (mysql_num_rows($result))

{
echo 'You already voted';
}
else
{

echo 'Go ahead and vote';

}

?>

Weedpacket

Still speaking generally, I thought I better clear up a misapprehension here:

Rodney H. wrote:
You are using an assignment operator "=", but assignment I think will always be true.

Not quite: the value of an assignment expression is the value of whatever was being assigned, so "$rs=5" evaluates to 5 and "$rs=0" evaluates to 0. (That's why statements like ($a = $b = $c; can work). It's that value that gets tested by the if statement to see if it's equivalent to true or false. In the latter example, 0 is equivalent to false, so if($rs=0) always fails.

Back to specifics. Taking the most recent version of the posted code, and sweeping up some of the discarded rubbish lying around, and then using

 tags around the code to save my eyesight, I get:
[code=php]@session_start();
require_once("engine.php");

// Checks if the user is authorized
if (!is_authorized())
{
	print "You must login before voting!";
	exit();
}

// Checks the item input
if (!check_item_id(@$_GET["id"]))
{
	print "Incorrect item id or missing";
	exit();
}

// Pick up the user ID of the user
$link = mysql_connect("localhost", "user", "pass") or die("Unable to connect to the database");
mysql_select_db("bestof");

$query = "select id FROM users where username= '".$_SESSION["username"]."'";
$rs_query=mysql_query($query,$link);
$rs=mysql_fetch_array($rs_query);

$userid = $rs['id'];
//echo $userid

$result = mysql_query("SELECT * FROM items WHERE id_user = '$userid' AND id_category = " . $_GET['id']) or exit(mysql_error());
if (mysql_num_rows($result))
{
	echo 'You already voted';
}
else
{
	echo 'Go ahead and vote';
}

I'd improve on Devinmke's code a bit; if you only want to see if there are rows, and you don't care about what they contain...

$result = mysql_query("SELECT COUNT(*) FROM items WHERE id_user = '$userid' AND id_category = " . $_GET['id']) or die(mysql_error());
if (mysql_result($result, 0)!=0)
{
	echo 'You already voted';
}
else
{
	echo 'Go ahead and vote';
}

Then again, if you're getting $userid from the database only so that it can be used in a database query....

$link = mysql_connect("localhost", "user", "pass") or die("Unable to connect to the database");
mysql_select_db("bestof");

$count_votes = mysql_query("
	SELECT
		COUNT(*)
	FROM
		items, users
	WHERE
		items.id_category = " . $_GET['id']."
		AND users.username = '".$_SESSION['username']."'
		AND items.id_user = users.id") or die(mysql_error());
if (mysql_result($count_votes, 0)!=0)
{
	echo 'You already voted';
}
else
{
	echo 'Go ahead and vote';
}

Which does look like the correct query to use.

Rodney_H_

I stand corrected. Thanks, Weedpacket.