How to Bitwise compare a String

Question

I am working on a function that takes in a series of permission strings, less than 255 characters and assigns them to an entity. Each string assigned is unique, but there a

Answer 1

I found an interesting solution but I am unsure if how logically correct it is because I am not very familiar with how PHP handles string data. I decided to cut away everything and try to do it straight without any hashing or assigning or whatnot and just do bitwise operations on strings. It seemed to work, but I am not sure I can prove my logic true enough.

$key1 = "Access to Black Box";
$key2 = "Managing Black Box";
$key3 = "Nothing too see here";
$key3a = "Nothingg B";
$key3b = "too see";
$glob = "";

$glob = $glob | $key1;
if(($glob & $key1) == $key1){echo "
Key one exists in glob: " . $glob;}

$glob = $glob | $key2;
if(($glob & $key2) == $key2){echo "
Key one exists in glob: " . $glob;}

if(($glob & $key3) == $key3){echo "
Key three exists in glob: " . $glob;}
else{echo "
Key three does not exists in glob: " . $glob;}

$glob = $glob | $key3;
if(($glob & $key3) == $key3){echo "
Key three exists in glob: " . $glob;}

if(($glob & $key3a) == $key3a){echo "
Key three a exists in glob: " . $glob;}

if(($glob & $key3b) == $key3b){echo "
Key three b exists in glob: " . $glob;} 
else{echo "
Key three b does not exists in glob: " . $glob;}

Outputs:

Key one exists in glob: Access to Black Box
Key two exists in glob: Mcoew{nwobnmckkbox
Key three does not exists in glob: Mcoew{nwobnmckkbox
Key three exists in glob: Oomowoomsooboze
Key three a exists in glob: Oomowoomsooboze
Key three b does not exists in glob: Oomowoomsooboze

So this works, but what would I be looking at collision wise? With key3a I showed that a string that has a combination of characters that match positions with characters in other keys I can get a false positive. But can I get around it with strict rules on the permission strings? Each resource type is named and each resource type has a limited number of associated permissions. So something like "Blog....Write Post", "Blog...Publish Post", "Blog....Moderate Post", "Podcast.......Upload", "Podcast.......Publish" to compensate for the increasing probability of a collision since string length has little impact on PHP's speed.