filter_var_array() の第2引数に渡す descriptor 配列を生成するための小さな helper 関数です。 filter_validation_descriptors() は標準の validation filter 用 descriptor を生成します。 filter_callback_descriptors() は FILTER_CALLBACK 用 descriptor を生成します。 アプリケーション側では FILTER_VALIDATE_* や FILTER_CALLBACK を直接書かず、検証ルール名と callback の対応だけを書けるようにします。 小規模サイトのフォームでは、生成した descriptor 配列を array_replace…

usage.php

<?php

$input = [
    'email' => 'taro@example.com',
    'age' => '17',
    'message' => '',
];

$descriptors = array_replace(
    filter_validation_descriptors([
        'email' => 'email',

        'age' => [
            'rule' => 'int',
            'options' => [
                'min_range' => 18,
                'max_range' => 120,
            ],
        ],
    ]),

    filter_callback_descriptors([
        'message' => 'validate_message',
    ]),
);

$result = filter_var_array($input, $descriptors);

var_dump($descriptors);
var_dump($result);

function validate_message(string $value): string|false
{
    if ($value === '') {
        return false;
    }

    if (mb_strlen($value, 'UTF-8') > 1000) {
        return false;
    }

    return $value;
}

validation.php

<?php

declare(strict_types=1);

/**
 * Build descriptors for validation filters.
 *
 * Input:
 *
 * [
 *     'email' => 'email',
 *     'age' => [
 *         'rule' => 'int',
 *         'options' => [
 *             'min_range' => 18,
 *             'max_range' => 120,
 *         ],
 *     ],
 * ]
 *
 * Output:
 *
 * [
 *     'email' => [
 *         'filter' => FILTER_VALIDATE_EMAIL,
 *     ],
 *     'age' => [
 *         'filter' => FILTER_VALIDATE_INT,
 *         'options' => [
 *             'min_range' => 18,
 *             'max_range' => 120,
 *         ],
 *     ],
 * ]
 */
function filter_validation_descriptors(array $rules): array
{
    $descriptors = [];

    foreach ($rules as $field => $spec) {
        if (!is_string($field)) {
            throw new InvalidArgumentException('Field name must be a string.');
        }

        $descriptors[$field] = filter_validation_descriptor($field, $spec);
    }

    return $descriptors;
}

/**
 * Build descriptors for FILTER_CALLBACK.
 *
 * Input:
 *
 * [
 *     'message' => 'validate_message',
 * ]
 *
 * Output:
 *
 * [
 *     'message' => [
 *         'filter' => FILTER_CALLBACK,
 *         'options' => 'validate_message',
 *     ],
 * ]
 */
function filter_callback_descriptors(array $callbacks): array
{
    $descriptors = [];

    foreach ($callbacks as $field => $callback) {
        if (!is_string($field)) {
            throw new InvalidArgumentException('Field name must be a string.');
        }

        if (!is_callable($callback)) {
            throw new InvalidArgumentException("Callback is not callable: {$field}");
        }

        $descriptors[$field] = [
            'filter' => FILTER_CALLBACK,
            'options' => $callback,
        ];
    }

    return $descriptors;
}

function filter_validation_descriptor(string $field, mixed $spec): array
{
    if (is_string($spec)) {
        return [
            'filter' => validation_filter_id($spec),
        ];
    }

    if (!is_array($spec)) {
        throw new InvalidArgumentException(
            "Validation rule spec must be a string or an array: {$field}"
        );
    }

    $rule = $spec['rule'] ?? null;

    if (!is_string($rule) || $rule === '') {
        throw new InvalidArgumentException(
            "Validation rule name must be a non-empty string: {$field}"
        );
    }

    $options = $spec['options'] ?? [];
    $flags = $spec['flags'] ?? 0;

    if (!is_array($options)) {
        throw new InvalidArgumentException("options must be an array: {$field}");
    }

    if (!is_int($flags)) {
        throw new InvalidArgumentException("flags must be an int: {$field}");
    }

    $descriptor = [
        'filter' => filter_validation_id($rule),
    ];

    if ($options !== []) {
        $descriptor['options'] = $options;
    }

    if ($flags !== 0) {
        $descriptor['flags'] = $flags;
    }

    return $descriptor;
}

function filter_validation_id(string $name): int
{
    return match ($name) {
        'email' => FILTER_VALIDATE_EMAIL,
        'int' => FILTER_VALIDATE_INT,
        'float' => FILTER_VALIDATE_FLOAT,
        'boolean', 'bool' => FILTER_VALIDATE_BOOL,
        'url' => FILTER_VALIDATE_URL,
        'ip' => FILTER_VALIDATE_IP,
        'domain' => FILTER_VALIDATE_DOMAIN,
        'mac' => FILTER_VALIDATE_MAC,
        'regexp', 'regex' => FILTER_VALIDATE_REGEXP,

        default => throw new InvalidArgumentException(
            "Unknown validation rule: {$name}"
        ),
    };
}