PHP浮点数的精度

理论

http://php.net/manual/zh/language.types.float.php

http://justjavac.com/codepuzzle/2012/11/02/codepuzzle-float-from-surprised-to-ponder.html

http://justjavac.com/codepuzzle/2012/11/11/codepuzzle-float-who-stole-your-accuracy.html

https://yq.aliyun.com/articles/44252

http://www.cnblogs.com/dongkang/archive/2016/09/03/5836899.html

http://blog.csdn.net/phpfenghuo/article/details/46369591