How to replace a value in array by another different value in PHP?

Question

I'm trying to find a way to replace any duplicated value but the only solution I have found so far is array_unique which doesn't really work for me as I need the duplicate to be replaced by another number which itself is not a duplicate.

 function generate_random_numbers($rows, $delimiter)
 {
     $numbers = array();

     for($i = 0; $i < $delimiter; $i++)
     {
         $numbers[$i] = rand(1, $rows);

         if(in_array($i, $numbers))
         {
            $numbers[$i] = rand(1, $row);
         }
     }
     return $numbers;
 }

 $numbers = generate_random_numbers(20, 10);

 print_r($numbers);

would anyone help me out on this one please?

I actually want all the numbers inside $numbers array to be different but within the $row range. array_unique will remove the numbers that repeat and I want to have the numbers in $delimiter. — Felipe Alarcon
– Felipe Alarcon, Commented Aug 14, 2015 at 17:14

Rizier123 · Accepted Answer · 2015-08-14 17:24:49Z

4

You can do this way easier and faster.

Just create an array for all possible numbers with range(). Then shuffle() the array and take an array_slice() as big as you want.

<?php

    function generate_random_numbers($max, $amount) {
        if($amount > $max)
            return [];

        $numbers = range(1, $max);
        shuffle($numbers);
        return array_slice($numbers, 0, $amount);
    }

    $numbers = generate_random_numbers(20, 10);
    print_r($numbers);

?>

And if you want to get 490 unique elements from a range from 1 - 500, 10'000 times:

My version: ~ 0.7 secs
Your version: Order 2 birthday cakes, you will need them.

edited Aug 14, 2015 at 17:24

answered Aug 14, 2015 at 17:12

Rizier123

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kainaw · Accepted Answer · 2015-08-14 17:12:20Z

1

You are inserting a random number and then, if it is already in the array (which it MUST be because you just inserted it), you use a new random number, which might be a duplicate. So, you have to get a number that is not a duplicate:

do {
    $num = rand(1,$rows);
} while(!in_array($num, $numbers));

Now, you know that $num is not in $numbers, so you can insert it:

$numbers[] = $num;

answered Aug 14, 2015 at 17:12

kainaw

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WhoIsJohnDoe · Accepted Answer · 2015-08-14 17:13:36Z

1

You were pretty close. The if-clause needs to be a loop, to get new random number.
(Also your in_array was slightly wrong)

function generate_random_numbers($rows, $delimiter) {
    $numbers = array();

    for($i = 0; $i < $delimiter; $i++) {
        do {
            $number = rand(1, $rows);
        }
        while(in_array($number, $numbers));

        $numbers[] = $number;
    }

    return $numbers;
 }

answered Aug 14, 2015 at 17:13

WhoIsJohnDoe

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