PHP If / ELSE或Switch / Case Statement

Question

我提供的输入可以是1或0

$no_required
$on_arrival
$schengen_visa
$uk_visa
$usa_visa

我有以下情况，我想向每个用户显示唯一的消息

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

其中ABCDEF是上述变量。 哪种是显示结果的最佳和优化方式。

Answer 1

你展示的条件可以很好地通过位掩码建模：

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

然后，您只需将单独的变量格式化为位掩码：

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

然后选择正确的信息：

echo $messages[$bitmask];

---

注意：在这里使用常量而不是幻数也是必须的，所以它看起来像这样：

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];

---

将整个事物包装在适当的类中，您将拥有一个漂亮，可读，可维护，可重用的业务逻辑：

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();

Answer 2

<?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
}

?>

Answer 3

我认为开关将是不错的选择：

$val=$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 .
}

Answer 4

小提示：

为什么不将所有这些二进制数转换为整数值，然后通过switch语句传递它们？

<?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
    }
?>