PHP魔术方法例如

Question

我从Zend PHP学习指南这个问题，并不能找到一个合适的解释...

<?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; 
?> 

据导游介绍，解决方案应为“b,c,A,B,C,c: CC,b,c,A,B,C”。我无法弄清楚为什么 - 也许你会这样做？我的本意是，$间的第一个电话>一会导致产生“一”，但显然是错误的...

Answer 1

由于__get()电话echo，一些数据在echo外类的输出前被调用。

通过与echo第一线步进，这是它如何被执行：

$m->a "A" is concatenated 
","  "," is concatenated 
$m->b "b," is echoed, "B" is concatenated 
","  "," is concatenated 
$m->c "c," is echoed, "C" is concatenated 
"m"  "," is concatenated 

在这一点上，b,c,已是echo版，和现在显示与A,B,Cm值的字符串。