trim()函数用来整理用户输入数据，如下显示：
$name=trim($name);
$email=trim($email);
tirm()函数可以去除字符串开始位置和结束位置的空格，并将结果字符串返回。默认情况下去除换行符（n）回车符(r)水平(t)和垂直制表符(x0b) 字符串结束符号()和空格。
以下是来自于手册
without the second parameter, rtrim() will strip these characters:
* (ascii 32 (0x20)), an ordinary space.
* t (ascii 9 (0x09)), a tab.
* n (ascii 10 (0x0a)), a new line (line feed).
* r (ascii 13 (0x0d)), a carriage return.
* (ascii 0 (0x00)), the nul-byte.
* x0b (ascii 11 (0x0b)), a vertical tab
example#1 usage example of rtrim()
上例将输出：
string(32) these are a few words :) ...
string(16) example string
string(11) hello world
string(30) these are a few words :) ...
string(26) these are a few words :)
string(9) hello wor
string(15) example string
函数explode() implode() join()
explode — 使用一个字符串分割另一个字符串
字符串的排序 strcmp() strcasecmp() strnatcmp()
在字符串中查找字符串 strstr() strchr() strrchr() stristr()
太多了，慢慢看手册