PHP常量：优点/缺点 [英] PHP Constants: Advantages/Disadvantages

问题描述

最近我一直习惯将整数值赋给常量，只是使用常量名作为识别其目的的方法。但是，在某些情况下，这需要在需要字符串表示时编写类似于typeToString（$ const）的函数。显然这是低效率和不必要的，但只是一个问题每一次，一会儿。

所以我的问题是，是否有任何其他权衡，我应该考虑？哪种情况被认为是更清洁/更符合标准？

情况1 :(不需要字符串版本时更快？）

  class Foo {
 const USER_TYPE_ADMIN = 0; 
 const USER_TYPE_USER = 1; 
 const USER_TYPE_GUEST = 2; 
 
 public $ userType = self :: USER_TYPE_ADMIN; 
 
 public function __construct（$ type）{
 $ this-> userType = $ type; 
} 
 
 public function typeToString（）{
 switch（$ this-> userType）{
 case self :: USER_TYPE_ADMIN：
 return'admin '; 
 break; 
 
 case self :: USER_TYPE_USER：
 return'user'; 
 break; 
 
 case self :: USER_TYPE_GUEST：
 return'guest'; 
 break; 
 
默认值：
 return'unknown'; 
 break; 
} 
} 
} 
 
 $ foo = new Foo（Foo :: USER_TYPE_GUEST）; 
 echo $ foo-> typeToString（）; 
 //显示guest
  

案例2：需要字符串版本）

  class Foo {
 const USER_TYPE_ADMIN ='admin'; 
 const USER_TYPE_USER ='user'; 
 const USER_TYPE_GUEST ='guest'; 
 
 public $ userType = self :: USER_TYPE_ADMIN; 
 
 public function __construct（$ type）{
 $ this-> userType = $ type; 
} 
} 
 
 $ foo = new Foo（Foo :: USER_TYPE_GUEST）; 
 echo $ foo-> userType（）; 
 //显示guest
  

解决方案

性能差异将是可以忽略不计，除非你存储了很多。
我会更简洁地写 toString（）方法：

  $ strings = array 
（
 self :: USER_TYPE_ADMIN =>'admin'，
 self :: USER_TYPE_USER =>'user'，
）; 
 
 if（！isset（$ strings [$ type]））
 return'unknown'; 
 
 return $ strings [$ type]; 
  

此外，您可以使 $ strings 数组a static 。

Lately I've been in the habit of assigning integer values to constants and simply using the constant name as a means of identifying its purpose. However, in some cases this has resulted in the need to write a function like typeToString($const) when a string representation is needed. Obviously this is inefficient and unneccesary, but is only an issue every once and a while.

So my question is, are there any other tradeoffs I should consider? Which case is considered to be cleaner/more standards-compliant? Also, is the performance difference negligable for most cases?

Case 1: (faster when a string version is not needed?)

class Foo {
    const USER_TYPE_ADMIN = 0;
    const USER_TYPE_USER = 1;
    const USER_TYPE_GUEST = 2;

    public $userType = self::USER_TYPE_ADMIN;

    public function __construct($type) {
        $this->userType = $type;
    }

    public function typeToString() {
        switch($this->userType) {
            case self::USER_TYPE_ADMIN:
                return 'admin';
                break;

            case self::USER_TYPE_USER:
                return 'user';
                break;

            case self::USER_TYPE_GUEST:
                return 'guest';
                break;

            default:
                return 'unknown';
                break;
        }
    }
}

$foo = new Foo(Foo::USER_TYPE_GUEST);
echo $foo->typeToString();
// Displays "guest"

Case 2:(faster/easier when a string version is needed)

class Foo {
    const USER_TYPE_ADMIN = 'admin';
    const USER_TYPE_USER = 'user';
    const USER_TYPE_GUEST = 'guest';

    public $userType = self::USER_TYPE_ADMIN;

    public function __construct($type) {
        $this->userType = $type;
    }
}

$foo = new Foo(Foo::USER_TYPE_GUEST);
echo $foo->userType();
// Displays "guest"

解决方案

The performance difference will be negligible unless you're storing a lot of them. I'd write the toString() method more concisely:

$strings = array
(
    self::USER_TYPE_ADMIN => 'admin',
    self::USER_TYPE_USER => 'user',
);

if (!isset($strings[$type]))
    return 'unknown';

return $strings[$type];

Also, you could make the $strings array a static.

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