Selecting a specific column in a row associated with a specific id - php

Question

I am running into a little trouble here, I did some searches on Google and Stackexchange to see if someone else had answered this before but it didn't turn up useful content so I am asking for some assistance. I have a column name that does exist in the database however, for some reason the query to MySQL keeps saying that the index by that column name does not exist (Undefined index:) is what I am getting but it is defines in the table so I thought maybe I could go about this another way by requesting the id first, then fetch associated column_name value with that specific id row. Then I want to return that to the variable $column_name to make use of the variable in my next query. Normally when I do $id = $_REQUEST['id']; I get the current id for the item being rendered in the browser. But this "column_name" keeps returning an undefined index error. Yet it exist in the DB just as the ID column does. Why can I call on one and not the other?
How can I call on the specified column_name associated with the id in $_REQUEST['id']; global variable?
In the DB you find:
id = "Value"
itemId = "Item ID"
CategoryName = "Category"
If I request ID 1, how can I fetch the associated CategoryName with that ID?
Thanks for your help!
$id = $_REQUEST['id'];
if(!empty($id)){
$column_name = $this->dbConnection->query("SELECT column_name FROM table //That is directly associated with $id");
}

Answer 1

Add the $id in a WHERE clause in the query:
$column_name = $this->dbConnection->query("SELECT CategoryName FROM table WHERE id = $id");
Also, remember to escape all parameters you send to the databse, without it $id would be vulnerable to SQL Injection attacks.
Good luck :)

Answer 2

I was able to fix this thanks to #frz3993 by adding categoryName={some cat name} to the dynamically generated link redirecting to the page in question while also making the category value dynamically generated as well.
The previous page needed a modification to the link such as
href="DynamicallyGeneratedLink.php?categoryName=%s&id=%s"
This was able to make the category name available for the $_REQUEST[]; variable to then use it to create a new dynamically generated link that would allow the visitors to go back to the previous full list of items in the category without having to use the back button.
Now the following code looks like
function backToCategoryList($dbConnection){
$categoryName = $_REQUEST['categoryName'];
if($r = $this->dbConnection->query("SELECT categoryName FROM table WHERE categoryName = '$categoryName' LIMIT 1")){
while($d = $r->fetch_assoc()){
printf("<i class=\"icon icon-th\"></i>", $d['link'], $d['categoryName']);
}
}
}