PHP 手册 字符串相关函数: 去除和填充:trim,str_pad, str_repeat, strlen; 大小写转换:strtoupper, strtolower, ucfirst, ucwords; 格式化:strlen. strrev, number_format, md5[字符串加密] include 'xxx.php'; | require. define[常量定义], var_dump[打印变量], isset[检查变量],setcookie[设置cookie]