filter_var()

(PHP 5 >= 5.2.0, PHP 7)

使用特定的过滤器过滤一个变量

说明

参数

待过滤的变量。注意：标量的值在过滤前，会被转换成字符串。

The ID of the filter to apply.TheTypes of filtersmanual page lists the available filters.

If omitted,FILTER_DEFAULTwill be used, which is equivalent toFILTER_UNSAFE_RAW. This will result in no filtering taking place by default.

一个选项的关联数组，或者按位区分的标示。如果过滤器接受选项，可以通过数组的"flags"位去提供这些标示。对于回调型的过滤器，应该传入callable。这个回调函数必须接受一个参数，即待过滤的值，并且返回一个在过滤/净化后的值。

返回值

Returns the filtered data,orFALSEif the filter fails.

范例

一个filter_var()的例子

以上例程会输出：

string(15) "bob@example.com"
bool(false)

参见

• filter_var_array() 获取多个变量并且过滤它们
• filter_input() 通过名称获取特定的外部变量，并且可以通过过滤器处理它
• filter_input_array() 获取一系列外部变量，并且可以通过过滤器处理它们
• Types of filters
• callback类型的信息

Pay attention that the function will not validate "not latin" domains.
if (filter_var('уникум@из.рф', FILTER_VALIDATE_EMAIL)) { 
  echo 'VALID'; 
} else {
  echo 'NOT VALID';
}

I found some addresses that FILTER_VALIDATE_EMAIL rejects, but RFC5321 permits: 

Here is how to use multiple flags (for those who learn better by example, like me): 

While getting familiar with filter_var( $var, FILTER_VALIDATE_INT ), I found interesting that 0 will be filtered out and therefore wont be considered as an int. Hope that helps someone not to be stuck ;)
N.B.: if you need to accept 0's, you could use is_int()

It might be wise to trim or sanitize (FILTER_SANITIZE_EMAIL) your email variable before validating to remove spaces:
filter_var(trim($email), FILTER_VALIDATE_EMAIL)

Here's a simple test using filter_var with FILTER_VALIDATE_URL.
(If you're using file_get_contents after this you will run into a problem, I was using: PHP 5.5.12 (cli))

The result is:
Valid URL
string(14) "a://google.com"

Some boolean conversions: 

I managed to get this to work with PHP 5.1.6 on CentOS 5 with minor difficulty.
1) Download the PECL filter package
2) Extract the tarball
3) phpize the directory
4) ./configure
5) make
6) filter-0.11.0/logical_filters.c:25:31: error: ext/pcre/php_pcre.h: No such file or directory
7) find / -name php_pcre.h
8) Make sure php-devel is installed
9) Edit filter-0.11.0/logical_filters.c and replace "ext/pcre/php_pcre.h" with the absolute path of php_pcre.h
10) make
11) make install
12) add "extension=filter.so" to php.ini
13) Restart Apache

"(comment)localpart@example.com"
is an invalid E-Mail address per RFC5322 (Appendix A.6.3):
"Also, the comments and white space throughout addresses, dates, and message identifiers are all part of the obsolete syntax."

One key thing to remember about filtering integers is that the value for the option max_range must be less than or equal to the value of PHP_INT_MAX.
filter_var($someVariable, FILTER_VALIDATE_INT, array('options' => array('min_range' => 1, 'max_range' => SOME_VALUE_GREATER_THAN_PHP_INT_MAX)));
This will fail even if $someVariable is a valid integer in the expected range.
This can show up when you are attempting to validate a potential key for an unsigned MySQL INT type (whose maximum value is 4294967295) on a 32-bit system, where the value of PHP_INT_MAX is 2147483647.

FILTER_VALIDATE_URL validates a url like http://www.

Note that only using FILTER_VALIDATE_URL to validate url's input may result in XSS:
$url = 'javascript://%0Aalert(document.cookie)';
if (filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED)) {
  echo 'click';
}
You should at least additionally check the actually used scheme.

Note: filter_var with filter=FILTER_VALIDATE_URL used parse_url function

FILTER_SANITIZE_EMAIL header injection test.

||%0A|%0D|bcc|to|cc|Content-Type|Mime-Type|

Many people, myself included, have found that the FILTER_VALIDATE_EMAIL does not actually properly work.
Below is a wrapper that I believe validates every legal routable address.

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