array shifting problem

[dwebb]

i have in a database a user, and a value. something along the lines of:

user/value
D1/1
D2/2
D3/3
etc etc

there is going to be a maximum of 8 values (1-8) but an unlimited number of users.

now i need a way of dynamically shifting the values from what is stored in the DB. Each shift of the value must be 2 places, so 1 -> 3, 2 -> 4, .... , 7 -> 1, 8 -> 2. I can do this once easily but if say i have to do 4 shifts of 2 (so the person in position 1 ends back up in position 1) i have no idea on how to get it done.

is there anyway to do this?

[Installer]

If I understand what you want to to correctly, you could put the user/value into an array with the user as the key ('D1' => 1, 'D2' => 2...), then use code something like this:

foreach ($arr as $key => $val) {
    $val += 2;
    if ($val > 8) {
        $val -= 8;
    }
    $arr[$key] = $val;
}

Edit: Or this:

foreach ($arr as $key => $val) {
    if (($arr[$key] += 2) > 8) {
        $arr[$key] -= 8;
    }
}

[dwebb]

Originally posted by Installer
If I understand what you want to to correctly, you could put the user/value into an array with the user as the key ('D1' => 1, 'D2' => 2...), then use code something like this:

foreach ($arr as $key => $val) {
    $val += 2;
    if ($val > 8) {
        $val -= 8;
    }
    $arr[$key] = $val;
}

Edit: Or this:

foreach ($arr as $key => $val) {
    if (($arr[$key] += 2) > 8) {
        $arr[$key] -= 8;
    }
}

[/B]

if i understand this correctly it does something along the lines of say key = 6 and has value b. simply shift the value b 2 key places up to 8. The problem is this only works for a little while. I want to be able to shift it multiple times. say i need to shift (each shift consisting of 2 key places) 10 times? the math works as long as the addition to the key value remains rather low, i think anyways.

this whole thing is doing my head in.

[Installer]

for ($i = 0; $i < $however_many_you_want; $i++) {
    foreach ($arr as $key => $val) { 
        if (($arr[$key] += 2) > 8) { 
            $arr[$key] -= 8; 
        } 
    }
}

Putting it into a function would be easiest:

function increment_value_by_2($arr)
{
    foreach ($arr as $key => $val) { 
        if (($arr[$key] += 2) > 8) { 
            $arr[$key] -= 8; 
        } 
    }
    return $arr;
}

// One time:
$array = increment_value_by_2($array);

// Several times:
for ($i = 0; $i < $however_many_you_want; $i++) {
    $array = increment_value_by_2($array);
}

[dwebb]

yeah, i just tried it by doing something along the lines of this:

$arr = array('1', '2', '3', '4', '5', '6', '7', '8') ;
$numbershifts = 3 ;
for($i='1'; $i<=$numbershifts; $i++) {
foreach ($arr as $key => $val) {
$val += 2;
if ($val > 8) {
$val -= 8;
}
$arr[$key] = $val;
}
}
echo $arr[0] ;

which did the trick. now how to practically implement it. haha

[Installer]

Well, at least you tried it. Now you know it works.