php如何查看变量是真实被引用

$var1 = ‘Hello World‘;
$var2 = ‘‘;

$var2 =&$var1;

debug_zval_dump(&$var1);

$a = "aaa";
    $b = & $a;

    //echo $b; //这里依然会输出aaa,用xdebug_debug_zval打印你就知道为什么了
    xdebug_debug_zval("b");

打印结果

&string(11) "Hello World" refcount(3) b:

(refcount=2, is_ref=1),

string

 ‘aaa‘ (length=3)