# Filters & Filter Functions

This extension filters data by either validating or sanitizing it. This is especially useful when the data source contains unknown (or foreign) data, like user supplied input. For example, this data may come from an HTML form.

# Validate Email Address

When filtering an email address filter_var() will return the filtered data, in this case the email address, or false if a valid email address cannot be found:

var_dump(filter_var('john@example.com', FILTER_VALIDATE_EMAIL));
var_dump(filter_var('notValidEmail', FILTER_VALIDATE_EMAIL));

Results:

string(16) "john@example.com"
bool(false)

This function doesn't validate not-latin characters. Internationalized domain name can be validated in their xn-- form.

Note that you cannot know if the email address is correct before sending an email to it. You may want to do some extra checks such as checking for a MX record, but this is not necessary. If you send a confirmation email, don't forget to remove unused accounts after a short period.

# Validating A Value Is An Integer

When filtering a value that should be an integer filter_var() will return the filtered data, in this case the integer, or false if the value is not an integer. Floats are not integers:

var_dump(filter_var('10', FILTER_VALIDATE_INT));
var_dump(filter_var('a10', FILTER_VALIDATE_INT));
var_dump(filter_var('10a', FILTER_VALIDATE_INT));
var_dump(filter_var(' ', FILTER_VALIDATE_INT));
var_dump(filter_var('10.00', FILTER_VALIDATE_INT));
var_dump(filter_var('10,000', FILTER_VALIDATE_INT));
var_dump(filter_var('-5', FILTER_VALIDATE_INT));
var_dump(filter_var('+7', FILTER_VALIDATE_INT));

Results:

int(10)
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)
int(-5)
int(7)

If you are expecting only digits, you can use a regular expression:

if(is_string($_GET['entry']) && preg_match('#^[0-9]+$#', $_GET['entry']))
    // this is a digit (positive) integer
else
    // entry is incorrect

If you convert this value into an integer, you don't have to do this check and so you can use filter_var.

# Validating An Integer Falls In A Range

When validating that an integer falls in a range the check includes the minimum and maximum bounds:

$options = array(
    'options' => array(
        'min_range' => 5,
        'max_range' => 10,
    )
);
var_dump(filter_var('5', FILTER_VALIDATE_INT, $options));
var_dump(filter_var('10', FILTER_VALIDATE_INT, $options));
var_dump(filter_var('8', FILTER_VALIDATE_INT, $options));
var_dump(filter_var('4', FILTER_VALIDATE_INT, $options));
var_dump(filter_var('11', FILTER_VALIDATE_INT, $options));
var_dump(filter_var('-6', FILTER_VALIDATE_INT, $options));

Results:

int(5)
int(10)
int(8)
bool(false)
bool(false)
bool(false)

# Validate a URL

When filtering a URL filter_var() will return the filtered data, in this case the URL, or false if a valid URL cannot be found:

URL: example.com

var_dump(filter_var('example.com', FILTER_VALIDATE_URL));
var_dump(filter_var('example.com', FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED));
var_dump(filter_var('example.com', FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED));
var_dump(filter_var('example.com', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));
var_dump(filter_var('example.com', FILTER_VALIDATE_URL, FILTER_FLAG_QUERY_REQUIRED));

Results:

bool(false)
bool(false)
bool(false)
bool(false)
bool(false)

URL: http://example.com

var_dump(filter_var('http://example.com', FILTER_VALIDATE_URL));
var_dump(filter_var('http://example.com', FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED));
var_dump(filter_var('http://example.com', FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED));
var_dump(filter_var('http://example.com', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));
var_dump(filter_var('http://example.com', FILTER_VALIDATE_URL, FILTER_FLAG_QUERY_REQUIRED));

Results:

string(18) "http://example.com"
string(18) "http://example.com"
string(18) "http://example.com"
bool(false)
bool(false)

URL: http://www.example.com

var_dump(filter_var('http://www.example.com', FILTER_VALIDATE_URL));
var_dump(filter_var('http://www.example.com', FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED));
var_dump(filter_var('http://www.example.com', FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED));
var_dump(filter_var('http://www.example.com', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));
var_dump(filter_var('http://www.example.com', FILTER_VALIDATE_URL, FILTER_FLAG_QUERY_REQUIRED));

Results:

string(22) "http://www.example.com"
string(22) "http://www.example.com"
string(22) "http://www.example.com"
bool(false)
bool(false)

URL: http://www.example.com/path/to/dir/

var_dump(filter_var('http://www.example.com/path/to/dir/', FILTER_VALIDATE_URL));
var_dump(filter_var('http://www.example.com/path/to/dir/', FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/', FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/', FILTER_VALIDATE_URL, FILTER_FLAG_QUERY_REQUIRED));

Results:

string(35) "http://www.example.com/path/to/dir/"
string(35) "http://www.example.com/path/to/dir/"
string(35) "http://www.example.com/path/to/dir/"
string(35) "http://www.example.com/path/to/dir/"
bool(false)

URL: http://www.example.com/path/to/dir/index.php

var_dump(filter_var('http://www.example.com/path/to/dir/index.php', FILTER_VALIDATE_URL));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php', FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php', FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php', FILTER_VALIDATE_URL, FILTER_FLAG_QUERY_REQUIRED));

Results:

string(44) "http://www.example.com/path/to/dir/index.php"
string(44) "http://www.example.com/path/to/dir/index.php"
string(44) "http://www.example.com/path/to/dir/index.php"
string(44) "http://www.example.com/path/to/dir/index.php"
bool(false)

URL: http://www.example.com/path/to/dir/index.php?test=y

var_dump(filter_var('http://www.example.com/path/to/dir/index.php?test=y', FILTER_VALIDATE_URL));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php?test=y', FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php?test=y', FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php?test=y', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php?test=y', FILTER_VALIDATE_URL, FILTER_FLAG_QUERY_REQUIRED));

Results:

string(51) "http://www.example.com/path/to/dir/index.php?test=y"
string(51) "http://www.example.com/path/to/dir/index.php?test=y"
string(51) "http://www.example.com/path/to/dir/index.php?test=y"
string(51) "http://www.example.com/path/to/dir/index.php?test=y"
string(51) "http://www.example.com/path/to/dir/index.php?test=y"

Warning: You must check the protocol to protect you against an XSS attack:

var_dump(filter_var('javascript://comment%0Aalert(1)', FILTER_VALIDATE_URL));
// string(31) "javascript://comment%0Aalert(1)"

# Sanitize filters

we can use filters to sanitize our variable according to our need.

Example

$string = "<p>Example</p>";
$newstring = filter_var($string, FILTER_SANITIZE_STRING);
var_dump($newstring); // string(7) "Example"

above will remove the html tags from $string variable.

# Validating Boolean Values

var_dump(filter_var(true, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // true
var_dump(filter_var(false, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // false
var_dump(filter_var(1, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // true
var_dump(filter_var(0, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // false
var_dump(filter_var('1', FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // true
var_dump(filter_var('0', FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // false
var_dump(filter_var('', FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // false
var_dump(filter_var(' ', FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // false
var_dump(filter_var('true', FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // true
var_dump(filter_var('false', FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // false
var_dump(filter_var([], FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // NULL
var_dump(filter_var(null, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // false

# Validating A Number Is A Float

Validates value as float, and converts to float on success.

var_dump(filter_var(1, FILTER_VALIDATE_FLOAT));
var_dump(filter_var(1.0, FILTER_VALIDATE_FLOAT));
var_dump(filter_var(1.0000, FILTER_VALIDATE_FLOAT));
var_dump(filter_var(1.00001, FILTER_VALIDATE_FLOAT));
var_dump(filter_var('1', FILTER_VALIDATE_FLOAT));
var_dump(filter_var('1.0', FILTER_VALIDATE_FLOAT));
var_dump(filter_var('1.0000', FILTER_VALIDATE_FLOAT));
var_dump(filter_var('1.00001', FILTER_VALIDATE_FLOAT));
var_dump(filter_var('1,000', FILTER_VALIDATE_FLOAT));
var_dump(filter_var('1,000.0', FILTER_VALIDATE_FLOAT));
var_dump(filter_var('1,000.0000', FILTER_VALIDATE_FLOAT));
var_dump(filter_var('1,000.00001', FILTER_VALIDATE_FLOAT));


var_dump(filter_var(1, FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var(1.0, FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var(1.0000, FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var(1.00001, FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1', FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1.0', FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1.0000', FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1.00001', FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1,000', FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1,000.0', FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1,000.0000', FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1,000.00001', FILTER_VALIDATE_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));

Results

float(1)
float(1)
float(1)
float(1.00001)
float(1)
float(1)
float(1)
float(1.00001)
bool(false)
bool(false)
bool(false)
bool(false)

float(1)
float(1)
float(1)
float(1.00001)
float(1)
float(1)
float(1)
float(1.00001)
float(1000)
float(1000)
float(1000)
float(1000.00001)

# Validate A MAC Address

Validates a value is a valid MAC address

var_dump(filter_var('FA-F9-DD-B2-5E-0D', FILTER_VALIDATE_MAC));
var_dump(filter_var('DC-BB-17-9A-CE-81', FILTER_VALIDATE_MAC));
var_dump(filter_var('96-D5-9E-67-40-AB', FILTER_VALIDATE_MAC));
var_dump(filter_var('96-D5-9E-67-40', FILTER_VALIDATE_MAC));
var_dump(filter_var('', FILTER_VALIDATE_MAC));

Results:

string(17) "FA-F9-DD-B2-5E-0D"
string(17) "DC-BB-17-9A-CE-81"
string(17) "96-D5-9E-67-40-AB"
bool(false)
bool(false)

# Sanitze Email Addresses

Remove all characters except letters, digits and !#$%&'*+-=?^_`{|}~@.[].

var_dump(filter_var('john@example.com', FILTER_SANITIZE_EMAIL));
var_dump(filter_var("!#$%&'*+-=?^_`{|}~.[]@example.com", FILTER_SANITIZE_EMAIL));
var_dump(filter_var('john/@example.com', FILTER_SANITIZE_EMAIL));
var_dump(filter_var('john\@example.com', FILTER_SANITIZE_EMAIL));
var_dump(filter_var('joh n@example.com', FILTER_SANITIZE_EMAIL));

Results:

string(16) "john@example.com"
string(33) "!#$%&'*+-=?^_`{|}~.[]@example.com"
string(16) "john@example.com"
string(16) "john@example.com"
string(16) "john@example.com"

# Sanitize Integers

Remove all characters except digits, plus and minus sign.

var_dump(filter_var(1, FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var(-1, FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var(+1, FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var(1.00, FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var(+1.00, FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var(-1.00, FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('1', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('-1', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('+1', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('1.00', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('+1.00', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('-1.00', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('1 unicorn', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('-1 unicorn', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var('+1 unicorn', FILTER_SANITIZE_NUMBER_INT));
var_dump(filter_var("!#$%&'*+-=?^_`{|}~@.[]0123456789abcdefghijklmnopqrstuvwxyz", FILTER_SANITIZE_NUMBER_INT));

Results:

string(1) "1"
string(2) "-1"
string(1) "1"
string(1) "1"
string(1) "1"
string(2) "-1"
string(1) "1"
string(2) "-1"
string(2) "+1"
string(3) "100"
string(4) "+100"
string(4) "-100"
string(1) "1"
string(2) "-1"
string(2) "+1"
string(12) "+-0123456789"

# Sanitize URLs

Sanitze URLs

Remove all characters except letters, digits and $-_.+!*'(),{}|^~[]`<>#%";/?😡&=

var_dump(filter_var('http://www.example.com/path/to/dir/index.php?test=y', FILTER_SANITIZE_URL));
var_dump(filter_var("http://www.example.com/path/to/dir/index.php?test=y!#$%&'*+-=?^_`{|}~.[]", FILTER_SANITIZE_URL));
var_dump(filter_var('http://www.example.com/path/to/dir/index.php?test=a b c', FILTER_SANITIZE_URL));

Results:

string(51) "http://www.example.com/path/to/dir/index.php?test=y"
string(72) "http://www.example.com/path/to/dir/index.php?test=y!#$%&'*+-=?^_`{|}~.[]"
string(53) "http://www.example.com/path/to/dir/index.php?test=abc"

# Sanitize Floats

Remove all characters except digits, +- and optionally .,eE.

var_dump(filter_var(1, FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var(1.0, FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var(1.0000, FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var(1.00001, FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1', FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1.0', FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1.0000', FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1.00001', FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1,000', FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1,000.0', FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1,000.0000', FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1,000.00001', FILTER_SANITIZE_NUMBER_FLOAT));
var_dump(filter_var('1.8281e-009', FILTER_SANITIZE_NUMBER_FLOAT));

Results:

string(1) "1"
string(1) "1"
string(1) "1"
string(6) "100001"
string(1) "1"
string(2) "10"
string(5) "10000"
string(6) "100001"
string(4) "1000"
string(5) "10000"
string(8) "10000000"
string(9) "100000001"
string(9) "18281-009"

With the FILTER_FLAG_ALLOW_THOUSAND option:

var_dump(filter_var(1, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var(1.0, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var(1.0000, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var(1.00001, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1.0', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1.0000', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1.00001', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1,000', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1,000.0', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1,000.0000', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1,000.00001', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));
var_dump(filter_var('1.8281e-009', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_THOUSAND));

Results:

string(1) "1"
string(1) "1"
string(6) "100001"
string(1) "1"
string(2) "10"
string(5) "10000"
string(6) "100001"
string(5) "1,000"
string(6) "1,0000"
string(9) "1,0000000"
string(10) "1,00000001"
string(9) "18281-009"

With the FILTER_FLAG_ALLOW_SCIENTIFIC option:

var_dump(filter_var(1, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var(1.0, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var(1.0000, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var(1.00001, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1.0', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1.0000', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1.00001', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1,000', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1,000.0', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1,000.0000', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1,000.00001', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));
var_dump(filter_var('1.8281e-009', FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_SCIENTIFIC));

Results:

string(1) "1"
string(1) "1"
string(1) "1"
string(6) "100001"
string(1) "1"
string(2) "10"
string(5) "10000"
string(6) "100001"
string(4) "1000"
string(5) "10000"
string(8) "10000000"
string(9) "100000001"
string(10) "18281e-009"

# Validate IP Addresses

Validates a value is a valid IP address

var_dump(filter_var('185.158.24.24', FILTER_VALIDATE_IP));
var_dump(filter_var('2001:0db8:0a0b:12f0:0000:0000:0000:0001', FILTER_VALIDATE_IP));
var_dump(filter_var('192.168.0.1', FILTER_VALIDATE_IP));
var_dump(filter_var('127.0.0.1', FILTER_VALIDATE_IP));

Results:

string(13) "185.158.24.24"
string(39) "2001:0db8:0a0b:12f0:0000:0000:0000:0001"
string(11) "192.168.0.1"
string(9) "127.0.0.1"

Validate an valid IPv4 IP address:

var_dump(filter_var('185.158.24.24', FILTER_VALIDATE_IP, FILTER_FLAG_IPV4));
var_dump(filter_var('2001:0db8:0a0b:12f0:0000:0000:0000:0001', FILTER_VALIDATE_IP, FILTER_FLAG_IPV4));
var_dump(filter_var('192.168.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_IPV4));
var_dump(filter_var('127.0.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_IPV4));

Results:

string(13) "185.158.24.24"
bool(false)
string(11) "192.168.0.1"
string(9) "127.0.0.1"

Validate an valid IPv6 IP address:

var_dump(filter_var('185.158.24.24', FILTER_VALIDATE_IP, FILTER_FLAG_IPV6));
var_dump(filter_var('2001:0db8:0a0b:12f0:0000:0000:0000:0001', FILTER_VALIDATE_IP, FILTER_FLAG_IPV6));
var_dump(filter_var('192.168.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_IPV6));
var_dump(filter_var('127.0.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_IPV6));

Results:

bool(false)
string(39) "2001:0db8:0a0b:12f0:0000:0000:0000:0001"
bool(false)
bool(false)

Validate an IP address is not in a private range:

var_dump(filter_var('185.158.24.24', FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE));
var_dump(filter_var('2001:0db8:0a0b:12f0:0000:0000:0000:0001', FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE));
var_dump(filter_var('192.168.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE));
var_dump(filter_var('127.0.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE));

Results:

string(13) "185.158.24.24"
string(39) "2001:0db8:0a0b:12f0:0000:0000:0000:0001"
bool(false)
string(9) "127.0.0.1"

Validate an IP address is not in a reserved range:

var_dump(filter_var('185.158.24.24', FILTER_VALIDATE_IP, FILTER_FLAG_NO_RES_RANGE));
var_dump(filter_var('2001:0db8:0a0b:12f0:0000:0000:0000:0001', FILTER_VALIDATE_IP, FILTER_FLAG_NO_RES_RANGE));
var_dump(filter_var('192.168.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_NO_RES_RANGE));
var_dump(filter_var('127.0.0.1', FILTER_VALIDATE_IP, FILTER_FLAG_NO_RES_RANGE));

Results:

string(13) "185.158.24.24"
bool(false)
string(11) "192.168.0.1"
bool(false)

# Syntax

mixed filter_var ( mixed $variable [, int $filter = FILTER_DEFAULT [, mixed $options ]] )

# Parameters

Parameter	Details
variable	Value to filter. Note that scalar values are converted to string internally before they are filtered.
---	---
filter	The ID of the filter to apply. The Types of filters manual page lists the available filters.If omitted, FILTER_DEFAULT will be used, which is equivalent to FILTER_UNSAFE_RAW. This will result in no filtering taking place by default.
---	---
options	Associative array of options or bitwise disjunction of flags. If filter accepts options, flags can be provided in "flags" field of array. For the "callback" filter, callable type should be passed. The callback must accept one argument, the value to be filtered, and return the value after filtering/sanitizing it.

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