PHP&引用变量
概念在 PHP 中引用意味着用不同的名字访问同一个变量内容。
定义方式
使用 & 符号
工作原理
http://i2.运维网.com/images/blog/201808/22/414fdfd7fcb02679739b5e328b6e662f.png
内存图例：
http://i2.运维网.com/images/blog/201808/22/8ebb0ce8b22dffb9c12705a5ab97b741.png
memory_get_usage()函数：
http://i2.运维网.com/images/blog/201808/22/60b5c0141b4c3f303bffe17895dcdc80.png
执行结果：
http://i2.运维网.com/images/blog/201808/22/125381806503c61df04b8a7df730682e.png
引用变量：
http://i2.运维网.com/images/blog/201808/22/7876ebf1fd7f0a9184b0d0fdb1dc424d.png
引用变量的内存占用结果：
http://i2.运维网.com/images/blog/201808/22/71b61ed2832ce10bc72b941da51a9005.png
zval 变量容器（一）
http://i2.运维网.com/images/blog/201808/22/9b2194c556b91357201da04444f043b4.png
http://i2.运维网.com/images/blog/201808/22/3c0a28da5d33417394c0d0179f7d9845.png
zval 变量容器（二）
http://i2.运维网.com/images/blog/201808/22/af0ddfe518fe0e1424aeaf863b65c827.png
http://i2.运维网.com/images/blog/201808/22/841ee5cab5fabe35a7fa0da3867a4b55.png
zval 变量容器（三）
http://i2.运维网.com/images/blog/201808/22/e68aa2f23c7c7cd9c48c5544797da88a.png
http://i2.运维网.com/images/blog/201808/22/18fcdba3714a7a0bd5970e2509d95a96.png
zval 变量容器（四）
http://i2.运维网.com/images/blog/201808/22/4ec0ca742233a1d40df4129e35bfa5dd.png
http://i2.运维网.com/images/blog/201808/22/13a2334e8684984bb37d592c0a0973ac.png
http://i2.运维网.com/images/blog/201808/22/fb62ae6de31fbb8e1d5f08ef1f560a29.png
end
// unset 只会取消引用，不会销毁空间
http://i2.运维网.com/images/blog/201808/22/98413a90b5d5b06d488d31e8d35da199.png
http://i2.运维网.com/images/blog/201808/22/2d773d1321a77945aecdffba42089c04.png
// 对象本身就是引用传值（clone()）
http://i2.运维网.com/images/blog/201808/22/98bf8638ea2b9439b01096e8c897d9b1.png
http://i2.运维网.com/images/blog/201808/22/bdf3c73d02df00b5f9c84e7016490ba0.png
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