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filter_var

PHP function Edit on GitHub ✎

(PHP 5 >= 5.2.0, PHP 7, PHP 8)

Filters a variable with a specified filter

Description

filter_var(mixed $value, int $filter = FILTER_DEFAULT, array|int $options = 0): mixed

Filter a variable using a FILTER_VALIDATE_* validation filters, a FILTER_SANITIZE_* sanitization filters, or a custom filter.

Parameters

value

Value to filter.

Warning

Scalar values are converted to string internally before they are filtered.

filter

The filter to apply. Can be a validation filter by using one of the FILTER_VALIDATE_* constants, a sanitization filter by using one of the FILTER_SANITIZE_* or FILTER_UNSAFE_RAW, or a custom filter by using FILTER_CALLBACK.

Note

The default is FILTER_DEFAULT, which is an alias of FILTER_UNSAFE_RAW. This will result in no filtering taking place by default.

options

Either an associative array of options, or a bitmask of filter flag constants FILTER_FLAG_*.

If the filter accepts options, flags can be provided by using the "flags" field of array.

Return Values

On success returns the filtered data. On failure false is returned, unless the FILTER_NULL_ON_FAILURE flag is used, in which case null is returned.

Examples

A filter_var() example

php
<?php
var_dump(filter_var('bob@example.com', FILTER_VALIDATE_EMAIL));
var_dump(filter_var('https://example.com', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));
?>

The above example will output:

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

Example validating entries of an array

php
<?php
$emails = [
    "bob@example.com",
    "test@example.local",
    "invalidemail"
];

var_dump(filter_var($emails, FILTER_VALIDATE_EMAIL, FILTER_REQUIRE_ARRAY));
?>

The above example will output:

output
array(3) {
  [0]=>
  string(15) "bob@example.com"
  [1]=>
  string(18) "test@example.local"
  [2]=>
  bool(false)
}

Example of passing an array for options

php
<?php

$options = [
    'options' => [
        'min_range' => 10,
    ],
    'flags' => FILTER_FLAG_ALLOW_OCTAL,
];

var_dump(filter_var('0755', FILTER_VALIDATE_INT, $options));
var_dump(filter_var('011', FILTER_VALIDATE_INT, $options));

?>

The above example will output:

output
int(493)
bool(false)

Providing flags either directly or via an array

php
<?php

$str = 'string';

var_dump(filter_var($str, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE));
var_dump(filter_var($str, FILTER_VALIDATE_BOOLEAN, ['flags' => FILTER_NULL_ON_FAILURE]));

?>

The above example will output:

output
NULL
NULL

Correctly checking the result of validation

php
<?php

$value = '0';

// Wrong: 0 is a valid integer, but it is falsy
if (!filter_var($value, FILTER_VALIDATE_INT)) {
    echo "Wrong check: '$value' rejected\n";
}

// Correct: compare strictly against false
if (filter_var($value, FILTER_VALIDATE_INT) === false) {
    echo "'$value' is not a valid integer\n";
} else {
    echo "'$value' is a valid integer\n";
}

?>

The above example will output:

output
Wrong check: '0' rejected
'0' is a valid integer

Checking the result of boolean validation

php
<?php

foreach (['yes', 'no', 'maybe'] as $value) {
    $result = filter_var($value, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE);

    // false is a valid result here, so check for null instead
    if ($result === null) {
        echo "'$value' is not a valid boolean\n";
    } else {
        echo "'$value' is ", var_export($result, true), "\n";
    }
}

?>

The above example will output:

output
'yes' is true
'no' is false
'maybe' is not a valid boolean

See Also

Source: reference/filter/functions/filter-var.xml · from the official PHP manual (php/doc-en)