是否可以在 PHP 中动态定义类属性值? [英] Is it possible to define a class property value dynamically in PHP?

问题描述

是否可以定义 PHP 类属性并使用同一类中的属性动态分配值?类似的东西:

Is it possible to define a PHP class property and assign the value dynamically using a property within the same class? Something like:

class user {
    public $firstname = "jing";
    public $lastname  = "ping";
    public $balance   = 10;
    public $newCredit = 5;
    public $fullname  = $this->firstname.' '.$this->lastname;
    public $totalBal  = $this->balance+$this->newCredit;

    function login() {
        //some method goes here!
    }
}

产量:

解析错误:语法错误，第 6 行出现意外的 '$this' (T_VARIABLE)

Parse error: syntax error, unexpected '$this' (T_VARIABLE) on line 6

上面的代码有什么问题吗?如果是这样，请指导我，如果不可能，那么有什么好方法可以做到这一点?

Is anything wrong in the above code? If so, please guide me and if it is not possible then what is a good way to accomplish this?

推荐答案

你可以像这样把它放到构造函数中:

You can put it into the constructor like this:

public function __construct() {
    $this->fullname  = $this->firstname.' '.$this->lastname;
    $this->totalBal  = $this->balance+$this->newCredit;
}

为什么你不能按照你想要的方式做呢?手册中的引述解释了这一点:

Why can't you do it the way you wanted? A quote from the manual explains it:

这个声明可能包括一个初始化，但是这个初始化必须是一个常数值——也就是说，它必须能够在编译时被评估并且不能依赖于运行——时间信息以便进行评估.

This declaration may include an initialization, but this initialization must be a constant value--that is, it must be able to be evaluated at compile time and must not depend on run-time information in order to be evaluated.

有关 OOP 属性的更多信息，请参阅手册:http://php.net/manual/en/language.oop5.properties.php

For more infromation about OOP properties see the manual: http://php.net/manual/en/language.oop5.properties.php

这篇关于是否可以在 PHP 中动态定义类属性值?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！