Question

我有以下代码（取自Zend认证练习）：

<?php
class Magic
{
    public $a = "A";
    protected $b = array("a" => "A", "b" => "B", "c" => "C");
    protected $c = array(1, 2, 3);

    public function __get($v)
    {
        echo "$v,";
        return $this->b[$v];
    }

    public function __set($var, $val)
    {
        echo "$var: $val,";
        $this->$var = $val;
    }
}

$m = new Magic();
echo $m->a ."," .$m->b ."," .$m->c .",";
$m->c = "CC";
echo $m->a ."," .$m->b ."," .$m->c;

这输出以下内容：

b,c,A,B,C,c: CC,b,c,A,B,C

我理解的大部分输出，但第一个回声声明我不知道 - 输出可能是从＆＃34; A＆＃34;？开始的。毕竟，a是一个公共属性，它被正确定义，因此__get不会被调用，即使它被调用，我仍然不知道它将如何输出＆＃34; b＆＃34;。< / p>

如果我将第一个echo语句更改为：

echo $m->a;

输出：

正如所料。因此值在（完整）echo语句中发生变化，可能与优先级有关。

真的对这个输出的完整解释感兴趣。谢谢！

Answer 1

你的专栏：

echo $m->a ."," .$m->b ."," .$m->c .",";

也可以这样写：

$text = $m->a ."," .$m->b ."," .$m->c .",";
echo $text;

如上所述，命令行为更清晰：

首先连接字符串，然后打印连接字符串：

$m->a  =>                             'A,' is added to string
$m->b  => __get() print 'b,'   then   'B,' is added to string
$m->c  => __get() print 'c,'   then   'C,' is added to string
echo   => print 'A,B,C' (concatenated string)

echo语句中的值更改

1 个答案: