说明：  PHP常用库函数 |判断一个编程语言的功能强弱，可以从他的库函数入手。一个较好的编程语言，必然有较强的库函数。
(PHP library functions used | to determine the function of a programming language, strong or weak, from the library functions start with him. A better programming language, is bound to have a strong library function.)