PHP魔術方法例如

Question

我從Zend PHP學習指南這個問題，並不能找到一個合適的解釋...

<?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; 
?> 

據導遊介紹，解決方案應爲「b,c,A,B,C,c: CC,b,c,A,B,C」。我無法弄清楚爲什麼 - 也許你會這樣做？我的本意是，$間的第一個電話>一會導致產生「一」，但顯然是錯誤的...

Answer 1

由於__get()電話echo，一些數據在echo外類的輸出前被調用。

通過與echo第一線步進，這是它如何被執行：

$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 

在這一點上，b,c,已是echo版，和現在顯示與A,B,Cm值的字符串。