[php] trim() 去掉 \r \n 等不必要字元

This function returns a string with whitespace stripped from the beginning and end of str. Without the second parameter, trim() 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.
* "\0" (ASCII 0 (0x00)), the NUL-byte.
* "\x0B" (ASCII 11 (0x0B)), a vertical tab.

reference:
http://php.net/manual/en/function.trim.php