1. string strstr($pattern,$needle,[true/false])
2. str_replace($target,$instead,$str,[count]);str_ireplace
3.string substr('abcdef',-1,1);返回字符串的子字符串
4.array explode(" ","piece1 piece2 piece3"); 分割成数组
5.strpos strchr strrchr
6 str_split()