variable variables!?!?

GoSharks

hi - i've just discovered variable variables (with help of the articles section and php.net) and have not been able to get it to work for me in my current situation.

$query = "SELECT DISTINCT firstname, lastname, q1, q2, q3, q4,
q5, q6, q7, q8, q9, q10, q11, q12, q13, q14,
q15, q16, q17, q18
FROM vday WHERE q1!='$row->q1' AND id!='$row->id'";
$result1 = mysql_query($query) or die ("Error in query: $query. " . mysql_error());
	if (mysql_num_rows($result1) > 0)
	{
	while($row2 = mysql_fetch_object($result1))			
	{
		$matches = 0;
		if ($row->q2==$row2->q2)
		{
			$matches++;
			$matches++;
		}
		if (abs($row->q2 - $row2->q2) == 1)
		{
			$matches++;
		}
		for ($i = 3; $i <= 18; $i++)
		{
			$one = ${"row->q".$i};
			$two = ${"row2->q".$i};
			if($one == $two)
				$matches++;
		}

inside the for loop is where im trying to get this to work for me. it isnt giving me any parse errors or anything, but instead it is doing the $matches++ statement for every loop when it is not supposed to....

Weedpacket

Well, I'm worried about your database design, but I can suggest a couple of things.

Fetch an array instead of an object, then the fields are $row['q'.$i] instead of $row->{'q'.$i} (there's the other suggestion).

GoSharks

i just changed it to fetch as arrays and used "$row['q'.$i]" - worked great. why do you suggest arrays instead of object? (im not too familar with the selection options)

about the db... basically this is for a program where it will compare one person's answers to a particular question to everybody elses answers and determines who is "most compatible" with each other. the q1-q18 slots in the db hold single digit int numbers... any suggestions/comments about what i have now?

thanks!

Weedpacket

Originally posted by GoSharks
i just changed it to fetch as arrays and used "$row['q'.$i]" - worked great. why do you suggest arrays instead of object? (im not too familar with the selection options)

Oh, just because using mixing object oriented syntax and non-OO syntax for things that are functionally identical introduces an extra bit of complication: if you're going to use an object you might as well go all-out on OO.[/b][/quote]

the q1-q18 slots in the db hold single digit int numbers... any suggestions/comments about what i have now?

Well, consider how much grief you're going to have if you ever want to add a nineteenth question. Search here and on the web on the subject of "database normalization" for details, but basically each answer to each question will end up getting its own row in a (three-field) table dedicated to the purpose (the other two fields identifying the person and the question).

ahundiak

Just in case you do want to stick with objects, try something like:

$row = new stdClass;
$row->xxx12 = 'value xxx12';
$q = 'xxx';
$i = 12;
echo $row->{$q . $i} . "\n";

Basically, put the {} around the instance variable name.

But, Weedpacket is certainly correct, your db design probably needs some work.