Simple array question

[jean-yves]

I'm sure that this is soooo easy. However, I've been scratching me head over it for a few days, staring blankly at the online PHP manual 😉

So... If I have an associative array thus (dummy data to illustrate problem):

$colours = array(
"R" => "RED",
"B" => "BLUE",
"Y" => "YELLOW",
"G" => "GREEN"
);

I then have a variable, $col that holds the current colour. The value of this is always known by the script.

What I would like to do is return the previous and next colour, so that if $col were "Y", the previous colour would be "B" and the next colour would be "G".

Ideally, I would like to loop around if I get to the start or end of the array, so that for example, if $col were "R", then the previous colour would be "G", whereas if $col were "G", the next colour would be "R".

I'm sure that it's a one or two liner that involves the prev() and next() functions, but I've gone utterly blank.

Any help welcome 🙂

thanks

[barand]

$colours = array( 
"R" => "RED", 
"B" => "BLUE", 
"Y" => "YELLOW", 
"G" => "GREEN" 
); 
$a = array_keys($colours);
$b = array_keys($a,"Y");
$i = $b[0];
echo $a[$i-1].' '.$a[$i+1]."<br>";

$a is an indexed array containing the colours key values.
$b is an array containing the index of the one you are looking for

Because $a is indexed, then finding prev and next is just a matter of +- 1. Of course you'll have to test for the wrapround condition.

hth

[jean-yves]

Excellent! Thanks very much, will try it out this weekend.

🙂

[jean-yves]

Actually, I couldn't wait, and I've just tried it out on my dev machine. Works a treat. Thankyou!