在PHP OOP中$ a =＆$ b，$ a = $ b和$ a = clone $ b之间的区别OOP

Question

PHP OOP中的$a = &$b,$a = $b和$b = clone $a之间的区别是什么？ $a是一个类的实例。

Answer 1

// $a is a reference of $b, if $a changes, so does $b.  
$a = &$b; 

// assign $b to $a, the most basic assign. 
$a = $b; 

// This is for object clone. Assign a copy of object `$b` to `$a`. 
// Without clone, $a and $b has same object id, which means they are pointing to same object. 
$a = clone $b; 

并检查与References，Object Cloning更多信息。

Answer 2

// $a has same object id as $b. if u set $b = NULL, $a would be still an object 
$a = $b; 

// $a is a link to $b. if u set $b = NULL, $a would also become NULL 
$a = &$b; 

// clone $b and store to $a. also __clone method of $b will be executed 
$a = clone $b; 

Answer 3

如果你不知道什么是ZVAL结构，什么是引用计数，is_ref在ZVAL结构有关，只是需要一些时间PHP's garbage collection。