可以在 PHP 的类中使用静态常量吗？

发布于 2024-09-12 03:49:55 字数 369 浏览 5 评论 0原文

我预计以下内容会起作用，但似乎没有。

<?php

class Patterns
{
    public static const EMAIL = "/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix";
    public static const INT = "/^\d+$/";
    public static const USERNAME = "/^\w+$/";
}

因为它会抛出这个错误：

syntax error, unexpected T_CONST, expecting T_VARIABLE

原文

I expected the following to work but it doesn't seem to.

<?php

class Patterns
{
    public static const EMAIL = "/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix";
    public static const INT = "/^\d+$/";
    public static const USERNAME = "/^\w+$/";
}

Because it throws this error:

syntax error, unexpected T_CONST, expecting T_VARIABLE

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满地尘埃落定 2024-09-19 03:49:59

您如何尝试访问常量？

我相信这会起作用：

echo Patterns::$EMAIL; //shows "/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-...."

如果你只是将其声明为静态。

How are you trying to access the constants?

I believe this would work:

echo Patterns::$EMAIL; //shows "/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-...."

If you just declare it as static.

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丑疤怪 2024-09-19 03:49:58

不，类常量不能标记为静态，也不能指定可见性。

http://php.net/manual/en/language.oop5.static.php

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木有鱼丸 2024-09-19 03:49:58

您不需要将它们声明为静态或公共。查看手册中的示例：

http://www.php。 net/manual/en/language.oop5.constants.php

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待天淡蓝洁白时 2024-09-19 03:49:57

您可以在类中使用 const，如下所示：

class Patterns {
    const EMAIL = "/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix";
    const INT = "/^\d+$/";
    const USERNAME = "/^\w+$/";
}

并且可以像这样访问 USERNAME const：

Patterns::USERNAME

You can use const in class like this:

class Patterns {
    const EMAIL = "/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix";
    const INT = "/^\d+$/";
    const USERNAME = "/^\w+$/";
}

And can access USERNAME const like this:

Patterns::USERNAME

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过度放纵 2024-09-19 03:49:57

在 PHP 中，static 和 const 是两个不同的东西。

const 表示类常量。它们与普通变量不同，因为它们前面没有“$”，并且前面不能有任何可见性修饰符（public、protected、private）。它们的语法：

class Test
{
    const INT = "/^\d+$/";
}

因为它们是恒定的，所以它们是不可变的。

静态表示同一类的对象之间共享的数据。该数据可以修改。一个例子是一个类，它跟踪任意时刻有多少个实例正在运行：

class HowMany
{
    private static $count = 0;

    public function __construct()
    {
        self::$count++;
    }

    public function getCount()
    {
        return self::$count;
    }

    public function __destruct()
    {
        self::$count--;
    }
}

$obj1 = new HowMany();
$obj2 = new HowMany();

echo $obj1->getCount();

unset($obj2);

echo $obj1->getCount();

In PHP, static and const are two different things.

const denotes a class constant. They're different than normal variables as they don't have the '$' in front of them, and can't have any visibility modifiers (public, protected, private) before them. Their syntax:

class Test
{
    const INT = "/^\d+$/";
}

Because they're constant, they're immutable.

Static denotes data that is shared between objects of the same class. This data can be modified. An example would be a class that keeps track of how many instances are in play at any one time:

class HowMany
{
    private static $count = 0;

    public function __construct()
    {
        self::$count++;
    }

    public function getCount()
    {
        return self::$count;
    }

    public function __destruct()
    {
        self::$count--;
    }
}

$obj1 = new HowMany();
$obj2 = new HowMany();

echo $obj1->getCount();

unset($obj2);

echo $obj1->getCount();

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春风十里 2024-09-19 03:49:57

它们不是静态常量，只是常量

class Patterns 
{ 
    const EMAIL = "/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix"; 
    const INT = "/^\d+$/"; 
    const USERNAME = "/^\w+$/"; 
} 

echo Patterns::EMAIL;

They're not static constants, just constants

class Patterns 
{ 
    const EMAIL = "/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix"; 
    const INT = "/^\d+$/"; 
    const USERNAME = "/^\w+$/"; 
} 

echo Patterns::EMAIL;

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