Switch Statement based on if variables in two tables match - php

Question

So I have a switch statement that I want to display one form or another based on if the id from one table has the matching foreign key in another table.
So far what I have tried is nesting one while statement into another which isn't working.
$subresult = mysqli_query($con,"SELECT * FROM tags GROUP BY tag");
$subresult2 = mysqli_query($con,"SELECT * FROM tag_subscribe WHERE uid = $uid");
while ($row = mysqli_fetch_array($subresult)) {
$tid = $row['tid'];
while ($row2 = mysqli_fetch_array($subresult2)) {
$tid2 = $row2['tid'];
}
if ($tid2 == $tid) {
$subbedup = 'yes';
} else {
$subbedup = 'no';
}
switch ($subbedup) {
case ('yes'):
echo "alternate html form goes here because $tid2 == $tid";
break;
case ('no'):
echo "html form goes here";
break;
}
}
So when this code is run, it only returns switch "no" except it will return one switch "yes" which just happens to be the last record of the second table that contains the foreign key. When I think about it, that makes sense as it will just keep running through this loop until it runs out of records in the table. So I spent about six minutes getting to this point and I have spent the last 6 hours trying to get it to work correctly without any luck.
So once again, fine people at SO, save me! Please and Thank you :)
So my question is: How would this be done correctly?

Answer 1

I'm not exactly sure of your database structure, so I'll improvise.
Given these sample tables and columns:
tags
id name
tag_subscriptions
user_id tag_id
The query below will loop through all tags. Each tag includes a subscribed column set to either "yes" or "no", depending on whether the current user is subscribed to that particular tag.
$sql="SELECT t.`id`, t.`name`, IF (ISNULL(ts.`tag_id`),'no','yes') AS `subscribed`
FROM `tags` t
LEFT JOIN `tag_subscriptions` ts ON (ts.`user_id`=$uid AND ts.`tag_id`=t.`id`)
WHERE 1;"
Then loop through all tags:
$q=mysql_query($sql) or die(mysql_error());
while ($row=mysql_fetch_assoc($q)) {
switch ($row['subscribed']) {
case 'yes'
// user is subscribed to this tag
break;
default:
// user is not subscribed to this tag
}
}
I think (hope) this is closer to what you're looking for.
http://sqlfiddle.com/#!2/58684/1/0

Answer 2

Sorry for using PDO as thats what i know, you can convert the idea to MYSQLi im sure.
$db = new PDO($hostname,$username,$password);
$arraySubTags = array();
$query = "SELECT tagID FROM tag_subscribe WHERE uid = :uid";
$statement = $db->prepare($query);
$statement->bindValue(':uid', $uid);
$statement->execute();
$subscribedTags = $statement->fetchAll(PDO::FETCH_ASSOC); //or loop with a while using fetch()
$statement->closeCursor();
foreach($subscribedTags as $sTag)
{
array_push($arraySubTags,$sTag);
}
$query = "SELECT * FROM tags GROUP BY tag";
$statement = $db->prepare($query);
$statement->execute();
$allTags = $statement->fetchAll(PDO::FETCH_ASSOC); //or loop with a while using fetch()
$statement->closeCursor();
foreach($allTags as $tag)
{
if(in_array($tag['tagID'], $arraySubTags))
{
echo "person is subscribed";
}else{ echo "person not subscribed";}
}

Answer 3

This code just checks whether the last tag checked is subscribed to - to check for each one you need to move the switch statement into the outer while loop, after the if..else bit that sets the $subbedup variable for the current tag.
Or you could make $subbedup an array, indexed by the tag id, if you need to keep the switch separate for some reason.