Trending: Microservices Architecture GuideMySQL Fundamentals for Backend DevelopersJava Backend Interview: The 15 Questions That Come UpRedis: Caching, Data Structures & PersistenceCache Patterns and Pitfalls

PHP 高级过滤器

Batch filtering with filter_var_array, FILTER_CALLBACK, and nested structures.

Intermediate
Key Points`filter_var_array` declares a whole form's rules in one place.

Batch filtering

PHP
<?php
$data = [
    "name"  => "Tom",
    "age"   => "25",
    "email" => "tom@example.com",
    "ip"    => "192.168.1.1",
    "site"  => "not a url",
];

$rules = [
    "name"  => ["filter" => FILTER_SANITIZE_SPECIAL_CHARS],
    "age"   => ["filter" => FILTER_VALIDATE_INT, "options" => ["min_range" => 18]],
    "email" => FILTER_VALIDATE_EMAIL,
    "ip"    => FILTER_VALIDATE_IP,
    "site"  => FILTER_VALIDATE_URL,
];

print_r(filter_var_array($data, $rules));
Output
Array
(
    [name] => Tom
    [age] => 25
    [email] => tom@example.com
    [ip] => 192.168.1.1
    [site] => 
)

site became an empty string (false cast to string). That is dangerous: failure is indistinguishable from empty. Add FILTER_NULL_ON_FAILURE to tell them apart.

PHP
<?php
$rules = [
    "site" => [
        "filter" => FILTER_VALIDATE_URL,
        "flags"  => FILTER_NULL_ON_FAILURE,
    ],
];

$r = filter_var_array(["site" => "not a url"], $rules);
var_dump($r["site"]);
var_dump(array_key_exists("site", $r));
Output
NULL
bool(true)

Required and missing

Missing keys come back as null without error. To distinguish missing from invalid, check array_key_exists first.

PHP
<?php
$input = ["email" => "bad@"];
$rules = ["email" => FILTER_VALIDATE_EMAIL, "age" => FILTER_VALIDATE_INT];

$clean = filter_var_array($input, $rules);
$errors = [];

foreach ($rules as $field => $_) {
    if (!array_key_exists($field, $input) || $input[$field] === "") {
        $errors[$field] = "$field 必填";
    } elseif ($clean[$field] === null || $clean[$field] === false) {
        $errors[$field] = "$field 格式不正确";
    }
}

print_r($errors);
Output
Array
(
    [email] => email 格式不正确
    [age] => age 必填
)

FILTER_CALLBACK

When built-ins fall short, FILTER_CALLBACK attaches your own function — good for normalisation like lowercasing or whitespace collapsing.

PHP
<?php
function normalize(string $v): string {
    return mb_strtolower(preg_replace("/\s+/u", " ", trim($v)));
}

$r = filter_var("  Hello   World  ", FILTER_CALLBACK, ["options" => "normalize"]);
echo $r, "\n";

// 用闭包
$slug = filter_var("Hello World 2023", FILTER_CALLBACK, [
    "options" => fn($v) => strtolower(str_replace(" ", "-", $v)),
]);
echo $slug, "\n";
Output
hello world
hello-world-2023
FILTER_CALLBACK never receives null — PHP returns null without calling. Handle null separately.

Nested arrays

filter_var_array handles one level. For deeper structures recurse or filter level by level.

PHP
<?php
$input = [
    "user" => ["name" => " Tom ", "email" => "tom@example.com"],
    "tags" => ["  php ", "web", ""],
];

function cleanValue(mixed $v): mixed {
    if (is_array($v)) {
        return array_map("cleanValue", $v);
    }
    return is_string($v) ? trim($v) : $v;
}

$clean = cleanValue($input);
print_r($clean);

$clean["tags"] = array_values(array_filter($clean["tags"], fn($t) => $t !== ""));
print_r($clean["tags"]);
Output
Array
(
    [user] => Array
        (
            [name] => Tom
            [email] => tom@example.com
        )

    [tags] => Array
        (
            [0] => php
            [1] => web
            [2] => 
        )

)
Array
(
    [0] => php
    [1] => web
)

A whole-form validator

PHP
<?php
function validateForm(array $in): array
{
    $rules = [
        "name"  => ["required" => true, "filter" => FILTER_SANITIZE_SPECIAL_CHARS],
        "email" => ["required" => true, "filter" => FILTER_VALIDATE_EMAIL],
        "age"   => ["required" => true, "filter" => FILTER_VALIDATE_INT,
                    "options" => ["min_range" => 18, "max_range" => 99]],
        "site"  => ["required" => false, "filter" => FILTER_VALIDATE_URL],
    ];

    $clean = filter_var_array($in, $rules);
    $errors = [];

    foreach ($rules as $field => $r) {
        $raw = trim((string)($in[$field] ?? ""));

        if ($r["required"] && $raw === "") {
            $errors[$field] = "$field 必填";
            continue;
        }
        if ($raw === "") {
            continue;
        }
        if ($clean[$field] === false || $clean[$field] === null) {
            $errors[$field] = "$field 格式不正确";
        }
    }

    return [$errors, $clean];
}

[$errors, $clean] = validateForm([
    "name" => "Tom", "email" => "tom@example.com", "age" => "17", "site" => "",
]);
print_r($errors);
print_r($clean);
Output
Array
(
    [age] => age 格式不正确
)
Array
(
    [name] => Tom
    [email] => tom@example.com
    [age] => 
    [site] => 
)

The rule table declares required and format in one place, so adding a field touches only the array. This is the core idea behind Laravel's and Symfony's validators.

filter_var_array ignores extra keys like required and only reads filter / flags / options. Pass the whole rule table directly — extracting just filter would drop the options range checks.

Friends & Partners

新华字典在线查字汉语词典成语大全歇后语大全古诗词鉴赏网络热词专业术语大全