php7.0.1.2-NTS变量引用解析

define('NL', "\r\n");

$v1 = 'shared';  //原始变量   //生成一个变量容器
xdebug_debug_zval('v1');  //(refcount=0, is_ref=0)string 'shared' (length=6)
$v2 = &$v1;  //引用计数加1
xdebug_debug_zval('v1');  //(refcount=2, is_ref=1)string 'shared' (length=6)
$v3 = &$v2;  //引用计数加1
xdebug_debug_zval('v1');  //(refcount=3, is_ref=1)string 'shared' (length=6)
$v4 = &$v3;  //引用计数加1
xdebug_debug_zval('v4');  //(refcount=4, is_ref=1)string 'shared' (length=6)
echo 'before:'.NL;
echo 'v1=' . $v1 . NL;
echo 'v2=' . $v2 . NL;
echo 'v3=' . $v3 . NL;
echo 'v4=' . $v4 . NL.'
';
//xdebug_debug_zval('v1');
//xdebug_debug_zval('v2');
// detach messy
$detach = $v1; //用$detach保存$v1 不同内存地址

xdebug_debug_zval('v1');     //(refcount=4, is_ref=1)string 'shared' (length=6)  //1234共享一个内存地址
xdebug_debug_zval('detach'); //(refcount=0, is_ref=0)string 'shared' (length=6)  //独立一个内存地址
unset($v1); //unset掉$v1 所以与 $v1关联得变量容器减1
xdebug_debug_zval('v1');  //(refcount=0, is_ref=0)*uninitialized* 未初始化
xdebug_debug_zval('v2');  //(refcount=3, is_ref=1)string 'shared' (length=6)  //234共享一个内存地址
$v1 = $detach;
xdebug_debug_zval('v1');  //(refcount=0, is_ref=0)string 'shared' (length=6)  //独立一个内存地址
// detach pretty, but slower
eval(detach('$v2'));  // 覆盖变量容器$detach  unset $v2
xdebug_debug_zval('v2');  //(refcount=0, is_ref=0)string 'shared' (length=6)  //此时v2为独立一个内存地址
xdebug_debug_zval('v3');  //(refcount=2, is_ref=1)string 'shared' (length=6)  //v3跟v4是同一内存地址
xdebug_debug_zval('v3');  //(refcount=2, is_ref=1)string 'shared' (length=6)  //v3跟v4是同一内存地址
$v1 .= '?';
$v2 .= ' no more';
$v3 .= ' stiooo';
$v4 .= 'll';

echo NL.'after:'.NL;
echo 'v1=' . $v1 . NL;
echo 'v2=' . $v2 . NL;
echo 'v3=' . $v3 . NL;
echo 'v4=' . $v4 . NL;

function detach($v) {
    $e = '$detach = ' . $v . ';';
    $e .= 'unset('.$v.');';
    $e .= $v . ' = $detach;';
    return $e;
}