Convert array to decimal - php

Question

I have this code:
public function get_names($number){
$names = array(
'None',
'Anton',
'bertha',
'Cesa',
'Dori',
'Egon',
'Frank',
'Gollum',
'Hans',
'Kane',
'Linus',
'Moose',
'Nandor',
'Oliver',
'Paul',
'Reese');
$bin = strrev(decbin($number));
$len = strlen($bin);
$output = array();
foreach(str_split($bin) as $key=>$char)
{
if ($key == sizeof($names)){
break;
}
if($char == 1)
{
array_push($output,$names[$key]);
}
}
return $output;
}
When I now call the function with number - let's say - 32256 I would get an array with "Kane, Linus, Moose, Nandor, Oliver, Paul".
Can anyone tell me what I would have to do when I want to give a certain names array and wanna get the number as a result where the certain bits are included? So exactly the other way around.
I found that code somewhere which works fine. But I need it vice versa.
Thanks in advance!
Andreas
EDIT: I want to know the decimal number when I e.g. have an array with "Anton, bertha,Cesa". I want to store those in a database instead of storing arrays with names each time. And when I need the names I just take the decimal number from database and use my function to get my name arrays.

Answer 1

If you just take the position in your $names array as being the bit position, you raise 2 to this position to give it the correct bit position and keep a running total of the items found...
$input = ["Cesa", "Gollum", "Hans"];
$output = 0;
foreach ( $input as $digit ) {
$output += pow(2,array_search($digit, $names ));
}
echo $output; // 392
with
$input = ["Kane", "Linus", "Moose", "Nandor", "Oliver", "Paul"];
gives
32256
Or as Barmar points out in his comment, you can save the lookup by inverting the names array using array_flip() which will mean that looking up each key will give the position in the array...
$output = 0;
$names = array_flip($names);
foreach ( $input as $digit ) {
$output += pow(2,$names[$digit]);
}
echo $output;