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Reference – What does this symbol mean in PHP?

I googled much for finding answer but i couldn’t find any.
I saw in few free source codes that they use “|” sign to combine values or something. can someone enlighten what is different between “|” and “+”?

sample:

<?php
define('PERMISSION_DENIED', 0);
define('PERMISSION_READ', 1);
define('PERMISSION_ADD',  2);
define('PERMISSION_UPDATE', 4);
define('PERMISSION_DELETE', 8);


$read_only = PERMISSION_READ;
$read_delete = PERMISSION_READ | PERMISSION_DELETE;
$full_rights = PERMISSION_DENIED | PERMISSION_READ | PERMISSION_ADD | PERMISSION_UPDATE | PERMISSION_DELETE;


$myrights = PERMISSION_READ;
$myrights |= PERMISSION_UPDATE; 
?>

why not just:

<?php
define('PERMISSION_DENIED', 0);
define('PERMISSION_READ', 1);
define('PERMISSION_ADD',  2);
define('PERMISSION_UPDATE', 4);
define('PERMISSION_DELETE', 8);


$read_only = PERMISSION_READ;
$read_delete = PERMISSION_READ + PERMISSION_DELETE;
$full_rights = PERMISSION_DENIED + PERMISSION_READ + PERMISSION_ADD + PERMISSION_UPDATE + PERMISSION_DELETE;


$myrights = PERMISSION_READ;
$myrights += PERMISSION_UPDATE; 
?>

Answer 1

it’s the bitwise or operator, so you’re operating with numbers in base 2 notation.

for example:

1000 | 0001 = 1001 ==> (8 | 1 = 9)

http://www.php.net/manual/en/language.operators.bitwise.php

In your code each permission is represented by one bit in a different position, I mean:

1 = 0001 = perm1
2 = 0010 = perm2
4 = 0100 = perm3
8 = 1000 = perm4

so doing or with those numbers gives you the number with all the permissions together. then if you wanna check if a permission is set you gotta do an and operation with the permission that you’re checking, for example:

$user_perms = perm1 | perm3;
if ($user_perms & perm4) echo "user does not have this permission";