(PHP 4 >= 4.0.4, PHP 5)ctype_alnum — Check for alphanumeric character(s)检测是否是只包含[A-Za-z0-9]ctype_alpha — Check for alphabetic character(s)检测是否是只包含[A-Za-z]ctype_cntrl — Check for control character(s)检查是否是只包含类是“”之类的字符控制字符ctype_digit — Check for numeric character(s)检查时候是只包含数字字符的字符串（0-9）ctype_