Programming Logic Question

[rghollenbeck]

(This question might need to go to a different forum, because it is more of a general programming logic question than a specific PHP question, but I don't know where else to ask.  I am writing the program in PHP, so this is the first place I thought of to ask.  If I need to move this question somewhere else, please advise.   Thanks.)

 

The short version (straight to the point):

I need to generate a list of non-sequential integers and then randomize that list.

 

 

The longer version:  

I am writing a Bible quiz program and the first page has an HTML form where the user selects a question category (i.e. a book from the Bible.)  Once that selection is made, Each question in the MySQL database has an auto-increment questionID (integer) and a categoryname (string) as well as a question and an answer and some other fields.

 

I will need to gather a list of QuestionIDs corresponding to the chosen category, then ask the questions from that category, one-at-a-time--preferably in a random order.

 

The QuestionID is auto-incremented and new questions from 66 categories (66 books in the Bible) will be added daily.

 

I know how to use the rand() function on sequential integers, but this list will not be sequential.  Perhaps when I run the for each loop, I can add some code to stuff an array with the QuestionID for each of these questions.  I could then randomize that array, put that array into a session variable, and then ask questions from that array of QuestionIDs.  Does that sound like a good solution?   That solution seems easier to ask than to code, but before attempting to tackle that idea, I thought it would be better to run it by some "PHP Freaks" first.  Better ideas out there?  Thanks.

Edited October 31, 2013 by rghollenbeck

[ignace]

$sql = 'SELECT QuestionId FROM Questions WHERE CategoryId = ?';

// prepare(), execute(), ...

$questionIds = $statement->fetchAll(PDO::FETCH_COLUMN, 0);

shuffle($questionIds);


// store in session

$_SESSION['question_ids'] = $questionIds;

$_SESSION['question_pos'] = 0;

[rghollenbeck]

shuffle($questionIds);

 

How awesome!  This function had my problem in mind exactly.  I was pondering how to randomize non-sequential integers--an impossible task.  Shuffle() solves this problem nicely.

 

Thank you ignace.

[AbraCadaver]

Why not just:

SELECT QuestionId FROM Questions WHERE CategoryId = ? ORDER BY RAND()

[rghollenbeck]

Thanks, AbraCadaver.  Good point.  I don't have to randomize the record numbers; randomizing the query results accomplishes the same thing.