PHP If/ELSE or Switch/Case Statement - PHP If/ELSE or Switch/Case Statement

我给出的输入可以是1或0

$no_required
$on_arrival
$schengen_visa
$uk_visa
$usa_visa

我有以下情况，我想为他们中的每一个显示唯一的消息返回给用户

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A、B、C、D、E、F为上述变量。这是最好的和优化的方式来显示结果

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  => ...
];

然后你只需要将你的单独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:使用常量而不是幻数在这里也是强制性的，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];

把整个东西包装在一个合适的类中，你就有了一个漂亮的、可读的、可维护的、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();

<?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
}
?>

我认为这是一个不错的选择:

$val=$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 .
}

小提示:

你为什么不把这些二进制数转换成整数值，然后通过switch语句传递它们呢?

<?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
    }
?>