multiple random numbers in php without repeating?

Question

I need four multiple random numbers without repeating. So i took an array for it. Can you help me where i have done wrong? I have 24 questions to come in random order, I need 4 questions per page, for this i took an array "$questions" and initially inserted 25 into it. then when ever i got a random number which is not in array, i am replacing that particular index with the random number. Where i have done wrong?

<?php
$questions = array(0);
for ($i = 0; $i < 24 ; $i++) {
$questions[$i]= ",";
}

$a="1";
$b="2";
$c="3";
$d="4";
//$a=rand(0, 23);
while(!in_array($a=rand(0, 23), $questions)) {
    $replacements = array($a => $a);
    $questions = array_replace($questions, $replacements);
    $max = sizeof($questions);
    if ($max==4) {
        break;
    }
    echo "<br>a=".$a."<br>";
    for ($i = 0; $i < 24 ; $i++) {
        echo $questions[$i];
    }
}
//echo "a=".$a."b=".$b."c=".$c."d=".$d;
?>

That's a whole lot of recurring code. Have you ever heard about DRY? — Zeta
– Zeta, Commented Mar 10, 2013 at 10:35

VolkerK · Accepted Answer · 2013-03-10 10:42:06Z

4

I'd suggest randomizing the complete array/set once then breaking it down into chunks and store those chunks (e.g. in $_SESSION).

<?php
$questions = data(); // get data
shuffle($questions); // shuffle data
$questions = array_chunk($questions, 4); // split into chunks of four
// session_start();
// $_SESSION['questions'] = $questions;
// on subsequent requests/scripts do not re-create $questions but retrieve it from _SESSION

// print all sets
foreach($questions as $page=>$set) {
    printf("questions on page #%d: %s\n", $page, join(', ', $set));
}

// print one specific set
$page = 2;
$set = $questions[$page];
printf("\n---\nquestions on page #%d: %s\r\n", $page, join(', ', $set));


// boilerplate function: returns example data
function data() {
    return array_map(function($e) { return sprintf('question #%02d',$e); }, range(1,24));
}

answered Mar 10, 2013 at 10:42

VolkerK

96.3k20 gold badges169 silver badges232 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

VolkerK Over a year ago

I honestly don't understand what you tried there. Maybe you should explain your algorithm.

RecklessSergio Over a year ago

finally i have implemented, your algo volkerk. Thank you.

casparjespersen · Accepted Answer · 2013-03-10 10:40:29Z

3

You could do something like this:

<?php

$archive = array();
$span = 23;
$amount = 4;
$i = 0;
while (true) {
    $number = rand(0, $span);             // generate random number
    if (in_array($number, $archive)) {    // start over if already taken
        continue;
    } else {
        $i++;
        $archive[] = $number;             // add to history
    }
    /*
      do magic with $number
    */
    if ($i == $amount) break;             // opt out at 4 questions asked
}

answered Mar 10, 2013 at 10:40

casparjespersen

3,9406 gold badges48 silver badges70 bronze badges

3 Comments

casparjespersen Over a year ago

.. but I actually like VolkerK's solution better.

RecklessSergio Over a year ago

Hmm. I am just trying to implement in my way. I am thankful to you guys for your answers. Thanks @Volkerk and Thanks to you also

RecklessSergio Over a year ago

Thank you @caspar. I have tried your logic and implemented volkrek

Collectives™ on Stack Overflow

multiple random numbers in php without repeating?

2 Answers 2

2 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related