Ernest, close but you have it reversed for my needs (i.e. true binary
form). Notice that my LSB is to the left, not right.
As Evan Nemerson pointed out to me, the decbin(), bindec(), Dec2Bin()
and Bin2Dec() functions shed some light. What I need is the equivillant
functions but with a way to flip the order of the bits from LSB to MSB.
I believe that is called "little endian" and "big endian"?
I've been playing with one function to convert my purchitem[] to a
decimal value, then use the decbin() to get a string, then reverse it...
Seems cumbersome but mebbe that's the solution?
function Array2Dec($array)
{
$decimal = 0;
while ( list($Key, $Val) = each($array) )
{
//notice the ($Val - 1) because
//our array starts at index 0, not 1
$decBit = pow(2, ($Val - 1));
$decimal += $decBit;
echo "<br>array[".$Key."] = ".$Val." :: ".$decBit;
}
return $decimal;
}
function reverseString($myString)
{
$charArray = preg_split('//', $myString, -1,
PREG_SPLIT_NO_EMPTY);
$revchars = array_reverse($charArray);
$revString = "";
while ( list($Key, $Val) = each($revchars) ) { $revString .=
$Val; }
return $revString;
}
> -----Original Message-----
> From: Ernest E Vogelsinger [mailto:ernest@;vogelsinger.at]
> Sent: Wednesday, November 06, 2002 1:28 AM
> To: [EMAIL PROTECTED]
> Subject: RE: [PHP] How do I convert an array into a mask?
>
>
> At 10:18 06.11.2002, Daevid Vincent said:
> --------------------[snip]--------------------
> >doesn't lend itself nicely to expansion, but may be my only
> way. I just
> >have a gut feeling that it can be automated somehow. To turn
> 1,3,4 into
> >10110 seems like there is some 'math' there that can work. I also
> --------------------[snip]--------------------
>
> It's quite easy using the left-shift operator "<<". Note that
> the function below only works for values 1-31 on 32bit systems.
>
> <?php
>
> function makebits(&$array)
> {
> $result = 0;
> foreach ($array as $seq) {
> if (is_numeric($seq)) {
> $i = 1 << ($seq-1);
> // assuming ID's are 1-based
> $result += $i;
> }
> }
> return $result;
> }
>
> $a = array(1,3,5,9); // 0001 0001 0101 = 0x115
> echo '<xmp>', sprintf('0x%x', makebits($a)), "\n</xmp>";
>
> ?>
--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
