PHP validation class for username, email, and password

Question

I'm relatively new to PHP OOP, currently I'm practising how to use it, however I am not really certain I'm building my classes correctly, I think perhaps I'm missing something out but I'm not entirely sure what, any advice would be appreciated

Class

class Validation 
{
 private 
 $password,
 $repeatPassword,
 $username,
 $email;
 private static
 $minPassword = 7,
 $confirmPassword,
 $minUsername = 3,
 $maxUsername = 14,
 $validEmail;
 public static function validateEmail($email)
 { 
 return (filter_var($email, FILTER_VALIDATE_EMAIL) != self::$validEmail);
 } 
 public static function validatePassword($password)
 {
 return(strlen($password) >= self::$minPassword);
 }
 public static function validatecheckbox($agree)
 {
 return(!empty($terms) >= self::$checked);
 }
 public static function validateRepeatPassword($repeatPassword,$password) 
 { 
 return $repeatPassword === $password; 
 } 
 public static function validateUsername($username)
 {
 return strlen($username) >= self::$minUsername 
 && (strlen($username)) <= self::$maxUsername 
 && (filter_var($username , FILTER_VALIDATE_REGEXP,["options"=> [ "regexp" => "/^[\p{L}0-9\s]+$/u"]]) == TRUE);
 }
}

Usage

 $errors = array();
 $fields = array( 
 'username' => array( 
 'validator' => 'validateUsername', 
 'message' => 'What is your username?' 
 ), 
 'email' => array( 
 'validator' => 'validateEmail', 
 'message' => 'Please enter a valid email', 
 ), 
 'password' => array( 
 'validator' => 'validatePassword', 
 'message' => 'Password must be a minimum of seven characters' 
 )
); 
if(!Validation::validateRepeatPassword($password, $repassword)) 
{ 
 $errors[] = ["name" => "repassword", "error" => "Passwords must match"]; 
}
foreach($post as $key => $value) 
 {
 if(isset($fields[$key])) 
 {
 if(!Validation::{$fields[$key]['validator']}($value)) 
 {
 $errors[] = ['name' => $key, 'error' => $fields[$key]['message']];
 }
 }
}

• confusedGibbon: Yes towards the bottom foreach($post as $key => $value) { if(isset($fields[$key]))

Answer 1

Well, your class is good and does what it is supposed to do, except in validalidatecheckbox() (you are using variables that doesn't exist).

Also I would do this changes:

• Remove this code (it's unused):

  private $password, $repeatPassword, $username, $email;

• Change this to constants, so you can use it elsewhere:

  private static $minPassword = 7, $confirmPassword, $minUsername = 3, $maxUsername = 14, $validEmail;

So your class should look like this:

class Validation
{
 const MIN_PASSWORD_LENGTH = 7;
 const MIN_USERNAME_LENGTH = 3;
 const MAX_USERNAME_LENGTH = 14;
 // rest of your code

Also, I strongly recommend you to check PSR-1 and PSR-2 to make your code look standard-like.

• confusedGibbon: Thank you I honestly wasn't sure if const would be be the correct thing to use, I will read over both links too