Simple contact form example

ContactFormHandler.php

<?php

class ContactFormHandler
{
    public function __construct(ContactFormTemplate $template, ContactFormValidator $validator, ContactFormMailer $mailer)
    {
        $this->template = $template;
        $this->validator = $validator;
        $this->mailer = $mailer;
    }
    
    public function display()
    {
        return $this->template->render();
    }
    
    public function process(array $input)
    {
        $this->template->setOldInput($input);
        if(!$this->validator->validate($input)) {
            $errors = $this->validator->getErrors();
            $this->template->setErrors($errors);
        } else {
            $sent = $this->mailer->sendContactEmail($input['email'], $input['name'], $input['subject'], $input['message']);
            if(!$sent) {
                $this->template->setErrors(['' => 'Unable to send your contact email. Please try again.']);
            }
        }
        return $this->template->render();
    }
}
    

ContactFormMailer.php

<?php

class ContactFormMailer()
{
    protected $receiver = 'foo@bar.com';
    
    public function sendContactEmail($fromEmail, $fromName, $subject, $message)
    {
        $fromName = strip_tags($fromName);
        $fromEmail = strip_tags($fromEmail);
        $subject = htmlspecialchars($subject);
        $message = htmlspecialchars($message);
        
        $headers = "From: $fromEmail";
        
        return mail($this->receiver, $subject, $message, $headers);
        }
    }
}

ContactFormTemplate.php

<?php

class ContactFormTemplate
{
    
    protected $oldInput = [];
    
    protected $errors = []
    
    public function __construct(array $errors = [], array $oldInput = [])
    {
        $this->setErrors($errors);
        $this->setOldInput($oldInput);
    }
    
    public function setOldInput(array $oldInput)
    {
        $this->oldInput = $oldInput;
        
        return $this;
    }
    
    public function setErrors(array $errors)
    {
        $this->errors = $errors;
        
        return $this;
    }
    
    public function render()
    {
        //I'm too lazy to write this part
    }
}

ContactFormValidator.php

<?php

class ContactFormValidator()
{
    protected $errors = [];
    
    protected $input = [];
    
    protected $ruleset = [
        'email'     => [true, 4, FILTER_SANITIZE_EMAIL],
        'name'      => [true, 2, null],
        'subject'   => [true, 2, null],
        'body'      => [true, 10, null]
    ]
    
    public function validate(array $input)
    {
        $this->input = $input;
        $this->errors = [];
        foreach($this->ruleset as $field => $rules) {
            list($required, $minLength, $filterType) = $rules;
            $this->validateField($field, $required, $minLength, $filterType);
        }
        return $this->isValid();
    }
    
    public function isValid()
    {
        return is_empty($this->errors);
    }
    
    protected function getInput($field)
    {
        return ( $this->hasInput($field) ) ? $this->input['email'] : null;
    }
    
    protected function hasInput($field) {
        return isset($this->input[$field]);
    }
    
    protected function addError($field, $message)
    {
        if(!isset($this->errors[$field])) {
            $this->errors[$field] = [];
        }
        $this->errors[$field][] = $message;
    }
    
    protected function validateField($field, $required = true, $minLength = 2, $filterType = null)
    {
        $value = $this->getInput($field);
        $valid = true;
        $error = null;
        if($required && $value === null) {
            $error = $field, 'This field is required.';
        } elseif(strlen($value) < $minLength) {
            $error = "This field must be at least [$minLength] characters long.";
        } elseif($filterType !== null && !filter_var($field, $filterType)) {
            $error = "This field must be formatted correctly.";
        }
        if($error) {
            $this->addError($field, $error);
            $valid = false;
        }
        return $valid;
    }
}

index.php

<?php

$handler = new ContactFormHandler(new ContactFormTemplate, new ContactFormValidator, new ContactFormMailer);

$process = ($_SERVER['REQUEST_METHOD'] == 'POST');

echo ($process) ? $handler->display() : $handler->process($_POST);