no repeating rand

[asmith]

hey guys 

 

how can i use rand finction to give me diffrent numbers each time ? never repeat a number twice ?

 

i mean NOT like this :

 

$a = rand(1,100)

$b =rand(1,100)

while ($a == $b)
{
$b = rand(1,100)
}

 

 

maybe this code is simple , but makes trouble when going for the 3rd number, what about the 20th number ?!!

[kenrbnsn]

You need to store any previously generated random numbers in an array and check newly generated numbers against those stored.

Something like:

<?php
$used = array();
$a = rand(1,100);
$used[] = $a;
$b = rand(1,100);
while (in_array($b,$used)) $b = rand(1,100);
$used[] = $b;
?>

 

Note: not tested.

 

Ken

 

[asmith]

yea i guess it would work ,

if the rand range is (1,200) 

and we have 1 to 199 in $a  array , would it takes time to rand and rand and rand till accidently find the number 200 ?

if the the rand range go higher ,the last numbers wouldn't take so long to be found ?

[PFMaBiSmAd]

If you have known range of numbers, it is better to generate a list of all the numbers, randomize the list, and delete numbers as they get used.

[asmith]

hmmm that means making an array with for exmaple 250 values ??? ! that take time !

if i get it  wrong ,can you show me some example codes please?

[PFMaBiSmAd]

Depending on what you are going to use this for, you will need to store the un-used values in a flat-file or mysql database.

 

To generate a range of values in an array, use the php range function - http://php.net/range

[asmith]

hmm ok  !

i thought this "no-repeating" rand is so simple that could have an individual function !  never thought of this much trouble !