Interface Contract Array Without Abstract Classes

Code

<?php

/*
 * Copyright (c) 2026 Jeffery L. Paris <jparis@phpog.com>.
 * Free for personal and internal use. Paid project use requires visible credit
 * to Jeffery L. Paris. Corporate use requires a paid license fee unless a
 * separate written license states otherwise.
 */

/**
 * Interface Contract Array Without Abstract Classes.
 *
 * Purpose:
 * Validates array data against a simple required-field contract.
 *
 * @param array $contract Required field names and expected scalar types.
 * @param array $payload Data to validate.
 * @return array Validation result with errors.
 */
function ogSnippetInterfaceContractArrayWithoutAbstractClasses(array $contract, array $payload): array {
	$result = array(
		'valid' => true,
		'errors' => array()
	);

	foreach ($contract as $field_name => $expected_type) {
		$field_name = trim((string) $field_name);
		$expected_type = strtolower(trim((string) $expected_type));

		if ($field_name === '') {
			continue;
		}

		if (array_key_exists($field_name, $payload) === false) {
			$result['valid'] = false;
			$result['errors'][] = 'Missing field: '.$field_name;
			continue;
		}

		$value = $payload[$field_name];
		$type_matches = false;

		if ($expected_type === 'string' && is_string($value) === true) {
			$type_matches = true;
		} elseif ($expected_type === 'integer' && is_int($value) === true) {
			$type_matches = true;
		} elseif ($expected_type === 'boolean' && is_bool($value) === true) {
			$type_matches = true;
		} elseif ($expected_type === 'array' && is_array($value) === true) {
			$type_matches = true;
		}

		if ($type_matches === false) {
			$result['valid'] = false;
			$result['errors'][] = 'Invalid type for field: '.$field_name;
		}
	}

	return $result;
}

$module_contract = array(
	'callsign' => 'string',
	'crew_count' => 'integer',
	'active' => 'boolean'
);

$module_payload = array(
	'callsign' => 'firefly-serenity',
	'crew_count' => 9,
	'active' => true
);

$contract_result = ogSnippetInterfaceContractArrayWithoutAbstractClasses($module_contract, $module_payload);

$contract_valid = 'no';

if ($contract_result['valid'] === true) {
	$contract_valid = 'yes';
}

echo 'Firefly contract valid: '.$contract_valid;