PHP If/ELSE or Switch/Case Statement

Question

I have give inputs which can be either 1 or 0

$no_required
$on_arrival
$schengen_visa
$uk_visa
$usa_visa

I have the Following Cases and i want to display unique message back to the user for each one of them

a b c d e
1 0 0 0 0   No Visa Required
0 1 0 0 0   Visa can be obtained on Arrival
0 0 1 0 0   You need Schengen Visa
0 0 0 1 0   You need UK visa
0 0 0 0 1   You need US visa
0 0 1 1 1   You need Either of the Visas
0 0 1 1 0   You need Schengen/UK visa
0 0 1 0 1   You need Schengen/US visa
0 0 0 1 1   You need USA/UK visa

Where A B C D E F are the above variables. Which is the best and optimized way to display the results.

How are you storing the data in your code, how about some code? (didnt mean to put this as answer) — Brock Hensley
– Brock Hensley, Commented Apr 2, 2013 at 12:08
Add the values up as binary values then run the switch on the addition, if my brain is working right there can't be two values the same. ie if a is 1 add to a variable total 1 if b is 1 add 2, if c is one add 4 then do your switch based on the value of total — Rick Calder
– Rick Calder, Commented Apr 2, 2013 at 12:10

deceze · Accepted Answer · 2013-04-03 08:49:30Z

17

The conditions you're showing can very nicely be modeled via bit masks:

$messages = [
    16 => 'No Visa Required',
    8  => 'Visa can be obtained ...',
    4  => ...
];

You then just have to format your separate variables into a bitmask:

$bitmask = ($no_required ? 16 : 0)
         | ($on_arrival  ? 8  : 0)
         | ...;

Then just pick the right message:

echo $messages[$bitmask];

Note: use of constants instead of magic numbers is pretty much mandatory here as well, so it'd look like this:

define('VISA_NONE',       1);
define('VISA_ON_ARRIVAL', 2);
...

$messages = [
    VISA_NONE         => 'No Visa Required',
    ...,
    VISA_US | VISA_UK => 'You need USA/UK visa'
];

// using multiplication instead of conditionals, as mentioned in the comments
$bitmask = $no_required * VISA_NONE
         | $on_arrival  * VISA_ON_ARRIVAL
         | ...;

echo $messages[$bitmask];

Wrap the whole thing in an appropriate class and you have yourself a nice, readable, maintainable, reusable piece of business logic:

class Visa {

    const NONE       = 1;
    const ON_ARRIVAL = 2;
    ...

    protected $messages = [];

    protected $visa;

    public function __construct() {
        $this->messages = [
            static::NONE            => 'No Visa Required',
            ...,
            static::US | static::UK => 'You need USA/UK visa'
        ];
    }

    /**
     * @param int  $type    One of the class constants.
     * @param bool $enabled Whether this type of visa is required.
     */
    public function set($type, $enabled) {
        $this->visa = $this->visa | $type * (int)(bool)$enabled;
    }

    public function getMessage() {
        return $this->messages[$this->visa];
    }

}


$visa = new Visa;
$visa->set($visa::NONE,       $no_required);
$visa->set($visa::ON_ARRIVAL, $on_arrival);

echo $visa->getMessage();

edited Apr 3, 2013 at 8:49

answered Apr 2, 2013 at 12:11

deceze♦

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10 Comments

jantimon Over a year ago

Hopefully I will never have to maintain such a mess ;)

Novak Over a year ago

If the values are either 0 or 1, can't you just multiply them by each power of 2? Instead of conditionals.

deceze Over a year ago

@Guy Sure, you could also left shift or do a couple of other tricks. I was going for the most obvious solution for somebody apparently not well versed in binary operations. :)

Novak Over a year ago

@deceze, I see, just wanted to point that out since the OP asked for an optimized solution.

Engineer Over a year ago

This is called overengineering:)

|

user1646111 · Accepted Answer · 2013-04-02 12:11:18Z

11

<?php
$messages = array('10000' => 'No Visa Required', '01000' => 'Visa can be obtained on Arrival');
$no_required = '0';
$on_arrival = '1';
$schengen_visa = '0';
$uk_visa = '0';
$usa_visa = '0';

$result = "$no_required$on_arrival$schengen_visa$uk_visa$usa_visa";
if(array_key_exists($result, $messages)){
 echo $messages[$result]; //Visa can be obtained on Arrival
}

?>

answered Apr 2, 2013 at 12:11

user1646111

Comments

Gurmeet · Accepted Answer · 2013-04-02 12:11:10Z

5

I think switch will be good option:

$val=$no_required.$on_arrival.$schengen_visa.$uk_visa.$usa_visa;

switch($val)
{
    case "10000":
        echo "No Visa Required";
        break;
    case "01000"   
        echo "Visa can be obtained on Arrival.";
        break;
    case "00100":
        echo "You need Schengen Visa";
        break;
         .
         .   //Continue to add cases .
}

answered Apr 2, 2013 at 12:11

Gurmeet

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Comments

user · Accepted Answer · 2013-04-02 12:41:19Z

3

A little tip:

Why don't you convert all those binary numbers into a integer value and then pass them through a switch statement?

<?php

    $integer_value = convert_binary_to_integer(a,b,c,d,e);

    // I'm not sure PHP provdies a function to convert binary numbers to integers number:
    // But you can write it yourself. It's pretty easy

    switch($integer_value) {
        case 16: // As the first combination of a,b,c,d,e corresponds to number 16 
             // do the appropriate action
        break;
            // ... and so on
    }
?>

edited Apr 2, 2013 at 12:41

user

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answered Apr 2, 2013 at 12:11

Arslan Ali

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