example of contact form

ajaxsend.php

<?php
/**
 * Created by PhpStorm.
 * User: xandros15
 * Date: 2017-03-31
 * Time: 02:26
 */
require_once __DIR__ . '/functions.php';

if ($errors = validateContactForm($_POST)) {
    http_response_code(400);
    header('Content-Type: application/json');

    echo json_encode(['data' => $errors], JSON_PRETTY_PRINT);
} else {
    if (sendMail($_POST)) {
        http_response_code(200);
    } else {
        http_response_code(500);
    }
}

composer.json

{
    "require": {
        "swiftmailer/swiftmailer": "^5.4",
        "respect/validation": "^1.1"
    }
}

composer.lock

{
    "_readme": [
        "This file locks the dependencies of your project to a known state",
        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
        "This file is @generated automatically"
    ],
    "hash": "703e671afc9e967b11afc2ad24e615bc",
    "content-hash": "62536cae59aa6ad837f15ec15c5e4898",
    "packages": [
        {
            "name": "respect/validation",
            "version": "1.1.12",
            "source": {
                "type": "git",
                "url": "https://github.com/Respect/Validation.git",
                "reference": "5ab87d1dd932872f6670136a513f72ff9ea41c67"
            },
            "dist": {
                "type": "zip",
                "url": "https://api.github.com/repos/Respect/Validation/zipball/5ab87d1dd932872f6670136a513f72ff9ea41c67",
                "reference": "5ab87d1dd932872f6670136a513f72ff9ea41c67",
                "shasum": ""
            },
            "require": {
                "php": ">=5.4",
                "symfony/polyfill-mbstring": "^1.2"
            },
            "require-dev": {
                "egulias/email-validator": "~1.2",
                "malkusch/bav": "~1.0",
                "mikey179/vfsstream": "^1.5",
                "phpunit/phpunit": "~4.0",
                "symfony/validator": "~2.6.9",
                "zendframework/zend-validator": "~2.3"
            },
            "suggest": {
                "egulias/email-validator": "Strict (RFC compliant) email validation",
                "ext-bcmath": "Arbitrary Precision Mathematics",
                "ext-mbstring": "Multibyte String Functions",
                "fabpot/php-cs-fixer": "Fix PSR2 and other coding style issues",
                "malkusch/bav": "German bank account validation",
                "symfony/validator": "Use Symfony validator through Respect\\Validation",
                "zendframework/zend-validator": "Use Zend Framework validator through Respect\\Validation"
            },
            "type": "library",
            "extra": {
                "branch-alias": {
                    "dev-master": "1.1-dev"
                }
            },
            "autoload": {
                "psr-4": {
                    "Respect\\Validation\\": "library/"
                }
            },
            "notification-url": "https://packagist.org/downloads/",
            "license": [
                "BSD Style"
            ],
            "authors": [
                {
                    "name": "Respect/Validation Contributors",
                    "homepage": "https://github.com/Respect/Validation/graphs/contributors"
                }
            ],
            "description": "The most awesome validation engine ever created for PHP",
            "homepage": "http://respect.github.io/Validation/",
            "keywords": [
                "respect",
                "validation",
                "validator"
            ],
            "time": "2017-03-14 09:44:11"
        },
        {
            "name": "swiftmailer/swiftmailer",
            "version": "v5.4.6",
            "source": {
                "type": "git",
                "url": "https://github.com/swiftmailer/swiftmailer.git",
                "reference": "81fdccfaf8bdc5d5d7a1ef6bb3a61bbb1a6c4a3e"
            },
            "dist": {
                "type": "zip",
                "url": "https://api.github.com/repos/swiftmailer/swiftmailer/zipball/81fdccfaf8bdc5d5d7a1ef6bb3a61bbb1a6c4a3e",
                "reference": "81fdccfaf8bdc5d5d7a1ef6bb3a61bbb1a6c4a3e",
                "shasum": ""
            },
            "require": {
                "php": ">=5.3.3"
            },
            "require-dev": {
                "mockery/mockery": "~0.9.1",
                "symfony/phpunit-bridge": "~3.2"
            },
            "type": "library",
            "extra": {
                "branch-alias": {
                    "dev-master": "5.4-dev"
                }
            },
            "autoload": {
                "files": [
                    "lib/swift_required.php"
                ]
            },
            "notification-url": "https://packagist.org/downloads/",
            "license": [
                "MIT"
            ],
            "authors": [
                {
                    "name": "Chris Corbyn"
                },
                {
                    "name": "Fabien Potencier",
                    "email": "fabien@symfony.com"
                }
            ],
            "description": "Swiftmailer, free feature-rich PHP mailer",
            "homepage": "http://swiftmailer.org",
            "keywords": [
                "email",
                "mail",
                "mailer"
            ],
            "time": "2017-02-13 07:52:53"
        },
        {
            "name": "symfony/polyfill-mbstring",
            "version": "v1.3.0",
            "source": {
                "type": "git",
                "url": "https://github.com/symfony/polyfill-mbstring.git",
                "reference": "e79d363049d1c2128f133a2667e4f4190904f7f4"
            },
            "dist": {
                "type": "zip",
                "url": "https://api.github.com/repos/symfony/polyfill-mbstring/zipball/e79d363049d1c2128f133a2667e4f4190904f7f4",
                "reference": "e79d363049d1c2128f133a2667e4f4190904f7f4",
                "shasum": ""
            },
            "require": {
                "php": ">=5.3.3"
            },
            "suggest": {
                "ext-mbstring": "For best performance"
            },
            "type": "library",
            "extra": {
                "branch-alias": {
                    "dev-master": "1.3-dev"
                }
            },
            "autoload": {
                "psr-4": {
                    "Symfony\\Polyfill\\Mbstring\\": ""
                },
                "files": [
                    "bootstrap.php"
                ]
            },
            "notification-url": "https://packagist.org/downloads/",
            "license": [
                "MIT"
            ],
            "authors": [
                {
                    "name": "Nicolas Grekas",
                    "email": "p@tchwork.com"
                },
                {
                    "name": "Symfony Community",
                    "homepage": "https://symfony.com/contributors"
                }
            ],
            "description": "Symfony polyfill for the Mbstring extension",
            "homepage": "https://symfony.com",
            "keywords": [
                "compatibility",
                "mbstring",
                "polyfill",
                "portable",
                "shim"
            ],
            "time": "2016-11-14 01:06:16"
        }
    ],
    "packages-dev": [],
    "aliases": [],
    "minimum-stability": "stable",
    "stability-flags": [],
    "prefer-stable": false,
    "prefer-lowest": false,
    "platform": [],
    "platform-dev": []
}

functions.php

<?php
/**
 * Created by PhpStorm.
 * User: xandros15
 * Date: 2017-03-31
 * Time: 01:06
 */
use Respect\Validation\Exceptions\NestedValidationException;
use Respect\Validation\Rules\Email;
use Respect\Validation\Rules\Length;
use Respect\Validation\Rules\StringType;
use Respect\Validation\Validator;

require_once __DIR__ . '/vendor/autoload.php';

/**
 * @param array $form
 *
 * @return array of errors
 */
function validateContactForm(array $form): array
{
    $errors = [];
    $rules  = [
        'email'   => (new Validator())->addRules([new Email()]),
        'subject' => (new Validator())->addRules([new StringType(), new Length(4, 24)]),
        'message' => (new Validator())->addRules([new StringType(), new Length(8, 255)]),
    ];

    foreach ($rules as $key => $validator) {
        /** @var $validator Validator */
        try {
            $validator->setName($key)->assert($form[$key] ?? null);
        } catch (NestedValidationException $exception) {
            $errors[$key] = $exception->getMessages();
        }
    }

    if (validateReCaptcha($form['g-recaptcha-response'] ?? '')) {
        $errors['g-recaptcha-response'][] = 'Zły kod recaptchy';
    }

    return $errors;
}

function validateReCaptcha(string $code): bool
{
    $url = 'https://www.google.com/recaptcha/api/siteverify?' . http_build_query([
            'secret'   => (require_once __DIR__ . '/settings.php')['reCaptcha']['secret'],
            'response' => $code,
        ]);

    return ($content = file_get_contents($url)) && ($response = json_decode($content, true)) && $response['success'];
}

function getMailer(): Swift_Mailer
{
    $config = (require_once __DIR__ . '/settings.php')['mailer'];

    $transport = new Swift_SmtpTransport($config['host'], $config['port']);
    $transport->setUsername($config['username']);
    $transport->setPassword($config['password']);

    return new Swift_Mailer($transport);
}

function prepareMail(array $params): Swift_Message
{
    $config = (require_once __DIR__ . '/settings.php')['mailer'];

    $mail = new Swift_Message(
        $params['subject'],
        $params['body'],
        'text/plain',
        'UTF-8'
    );

    $mail->setFrom($params['recipient']);
    $mail->setReplyTo($params['recipient']);
    $mail->setTo($config['email']);

    return $mail;
}

function sendMail(array $params): bool
{
    $mailer = getMailer();

    //we can parse message
    $params['body']      = $params['message'];
    $params['recipient'] = $params['email'];
    unset($params['message'], $params['email']);//free memory

    return (bool) $mailer->send(prepareMail($params));
}

send.php

<?php
/**
 * Created by PhpStorm.
 * User: xandros15
 * Date: 2017-03-31
 * Time: 01:06
 */

require_once __DIR__ . '/functions.php';

if ($errors = validateContactForm($_POST)) {
    $_SESSION['errors'] = $errors;
    header('Location: /', 302); //redirect to form ofc
} else {
    if (sendMail($_POST)) {
        $_SESSION['alert'] = [
            'message' => 'Wiadomość została wysłana',
            'type'    => 'success'
        ];
    } else {
        $_SESSION['alert'] = [
            'message' => 'Usługa czasowo niedostępna',
            'type'    => 'error'
        ];
    }
}

settings.php

<?php
/**
 * Created by PhpStorm.
 * User: xandros15
 * Date: 2017-03-31
 * Time: 01:18
 */

return [
    'reCaptcha' => [
        'secret' => '',
    ],
    'mailer'    => [
        'host'     => '',
        'port'     => '',
        'username' => '',
        'password' => '',
        'email'    => '',
    ],
];