delete a number in a comma seperated string

[JordashTalon]

I have a string like this:

12,18,4

Let's say I want to delete the 18 out of the string so it's like this:

12,4

What would be a good way to do that?

Also I need to do an add but only if the number is not already in the string,

So I have

12,18,4

And I try to add 18

it should fail because 18 is already there but if I try and add 9 it will add it on

12,18,4,9 (I already got this part working)

[oddz]

$nums = '12,18,4';
$s = array_search(18,explode(',',$nums));
if($s!==false) unset($nums[$s]); 

[oddz]

Probably how I would handle the second part.

<?php
$nums = '2,4,5,78,90';
$add = array(2,4,5,6,7);
$saved = explode(',',$nums);
$diff = array_diff($add,$saved);
if(!empty($diff)) $saved = array_merge($saved,$diff);
$nums = implode(',',$saved);
echo '<p>',$nums,'</p>';
?>

[JordashTalon]

thanks, that helped alot