PHP, Bitwise operators and using inclusive or as a parameter for enabling options

Question

Is there a way of defining some variables with true or false and passing them in collectively into a function as a parameter like in C++ like flags to turn sections of a function on or off using the bitwise inclusive or... For example:

// Declare

define( "ADMIN", TRUE);
define( "CLIENT", TRUE);

function Authenticated( $flags )
{
    // Not sure what would go here ? but something like
    // If ADMIN then
    // If CLIENT then
    // If ADMIN | CLIENT then
}

// Call

Authenticated( ADMIN | CLIENT );

Jon · Accepted Answer · 2013-06-10 16:45:20Z

0

You can define constants in your class and make sure their values are separate bits:

class Authentication
{
    const ADMIN  = 0x0001;
    const CLIENT = 0x0002;
}

function Authenticated($flags)
{
    $adminFlag = $flags & Authentication::ADMIN;
    $clientFlag = $flags & Authentication::CLIENT;

    if ($adminFlag && $clientFlag) ...
    else if ($adminFlag) ...
    else if ($clientFlag) ...
}

answered Jun 10, 2013 at 16:45

Jon

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4 Comments

Jimmyt1988 Over a year ago

Jon or anyone, why did you do 4 places for the bit number you put in? I know you can put 1, 2, 4, 6 etc and that is bad because it does not suggest you will use as bit fields.. but 0x1, 0x2, 0x4, 0x6 work too... was there any reason why you decided to prefix the 3 0's?

Jon Over a year ago

@JamesT: I just like having everything nicely lined up, and 4 digits 16 flags) is a good compromise between not writing too much and not leaving enough room to expand later. Just preference.

Jimmyt1988 Over a year ago

thanks mate :) - I just applied the same methodology to some javascript!!! I didn't know you could declare bit variables lol!

pjvleeuwen Over a year ago

Alternatively, binary integer literals are available since PHP 5.4.0, allowing to use 0b0001, 0b0010, 0b0100. Flags must be powers of 2 in order to bitwise-or together properly. So slight correction on the comment above, that is 0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, etc. Alternatively you can use the bitwise shift operator like 1<<0, 1<<1, 1<<2, 1<<3, 1<<4, 1<<5, 1<<6, 1<<7, 1<<8, 1<<9, 1<<10, 1<<11, etc...

Community · Accepted Answer · 2017-05-23 11:43:17Z

0

define("ADMIN", 0x0001);
define("CLIENT", 0x0002);

And now you can use them as actual bitflags.

edited May 23, 2017 at 11:43

CommunityBot

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answered Jun 10, 2013 at 16:44

Ignacio Vazquez-Abrams

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1 Comment

Jimmyt1988 Over a year ago

can you supply an example? I can then beaver away at it :D

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