Validate filters

**Listing of filters for validation**
ID	Name	Options	Flags	Description
`FILTER_VALIDATE_BOOLEAN`	"boolean"	`default`	`FILTER_NULL_ON_FAILURE`	Returns `TRUE` for "1", "true", "on" and "yes". Returns `FALSE` otherwise. If `FILTER_NULL_ON_FAILURE` is set, `FALSE` is returned only for "0", "false", "off", "no", and "", and `NULL` is returned for all non-boolean values.
`FILTER_VALIDATE_DOMAIN`	"validate_domain"	`default`	`FILTER_FLAG_HOSTNAME`	Validates whether the domain name label lengths are valid. Validates domain names against RFC 1034, RFC 1035, RFC 952, RFC 1123, RFC 2732, RFC 2181, and RFC 1123. Optional flag `FILTER_FLAG_HOSTNAME` adds ability to specifically validate hostnames (they must start with an alphanumeric character and contain only alphanumerics or hyphens).
`FILTER_VALIDATE_EMAIL`	"validate_email"	`default`	`FILTER_FLAG_EMAIL_UNICODE`	Validates whether the value is a valid e-mail address. In general, this validates e-mail addresses against the syntax in RFC 822, with the exceptions that comments and whitespace folding and dotless domain names are not supported.
`FILTER_VALIDATE_FLOAT`	"float"	`default`, `decimal`, `min_range`, `max_range`	`FILTER_FLAG_ALLOW_THOUSAND`	Validates value as float, optionally from the specified range, and converts to float on success.
`FILTER_VALIDATE_INT`	"int"	`default`, `min_range`, `max_range`	`FILTER_FLAG_ALLOW_OCTAL`, `FILTER_FLAG_ALLOW_HEX`	Validates value as integer, optionally from the specified range, and converts to int on success.
`FILTER_VALIDATE_IP`	"validate_ip"	`default`	`FILTER_FLAG_IPV4`, `FILTER_FLAG_IPV6`, `FILTER_FLAG_NO_PRIV_RANGE`, `FILTER_FLAG_NO_RES_RANGE`	Validates value as IP address, optionally only IPv4 or IPv6 or not from private or reserved ranges.
`FILTER_VALIDATE_MAC`	"validate_mac_address"	`default`		Validates value as MAC address.
`FILTER_VALIDATE_REGEXP`	"validate_regexp"	`default`, `regexp`		Validates value against `regexp`, a Perl-compatible regular expression.
`FILTER_VALIDATE_URL`	"validate_url"	`default`	`FILTER_FLAG_SCHEME_REQUIRED`, `FILTER_FLAG_HOST_REQUIRED`, `FILTER_FLAG_PATH_REQUIRED`, `FILTER_FLAG_QUERY_REQUIRED`	Validates value as URL (according to » http://www.faqs.org/rfcs/rfc2396), optionally with required components. Beware a valid URL may not specify the HTTP protocol `http://` so further validation may be required to determine the URL uses an expected protocol, e.g. `ssh://` or `mailto:`. Note that the function will only find ASCII URLs to be valid; internationalized domain names (containing non-ASCII characters) will fail.

Note:
As of PHP 5.4.11, the numbers +0 and -0 validate as both integers as well as floats (using FILTER_VALIDATE_FLOAT and FILTER_VALIDATE_INT). Before PHP 5.4.11 they only validated as floats (using FILTER_VALIDATE_FLOAT).

When default is set to option, default's value is used if value is not validated.

更新日志

版本	说明
7.4.0	Added `min_range` and `max_range` options for `FILTER_VALIDATE_FLOAT`.
7.0.0	Added `FILTER_FLAG_HOSTNAME`
5.5.0	Added `FILTER_VALIDATE_MAC`
5.2.1	`FILTER_VALIDATE_URL` now implicitly uses `FILTER_FLAG_SCHEME_REQUIRED` and `FILTER_FLAG_HOST_REQUIRED`.