Question

下面提到的代码有什么问题？它正在抛出解析错误 PHP解析错误：语法错误，意外'。'，期待'，'或';'在/home/gaurav/c.php第9行

<?php

class b {
    const ABC = 'abc';
}

class c extends b {

    private $r = self::ABC ." d";
    function getABC()
    {
            echo $this->r;
    }
}

$c = new c();
$c->getABC();

Answer 1

您可以尝试：

private $r = self::ABC;
$r = $r . "d";

Answer 2

此错误的原因是PHP不允许类成员声明中的表达式，即使只使用常量元素。

所以private $r = self::ABC ." d";是不允许的，而private $r = self::ABC;是可以的，因为Gautam3164已经回答了。

更多细节，例如在这个答案中： Initializing PHP class property declarations with simple expressions yields syntax error

Answer 3

从http://www.php.net/manual/en/language.oop5.properties.php

得到答案

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.

所以，在我的代码self :: ABC中。“d”不是常数。

php常量在类的数据成员中

3 个答案: