html - Php registration error validation -

i have been practicing php , mongodb. developing simple web application using oop.

i created class called user has methods user adduser, deleteuser etc. add user, form carry out simple validation tasks, not sure how. here class add new user:

function createuser($username, $name, $email, $password){               $user = array(                 'username' => $username,                 'name' => $name,                 'email' => $email,                 'password' => $password              );              if ($this->db->count(array('username' => $username)) == 0) {                 $this->db->insert($user);                 return true;              } else {                 echo 'username taken';             }        } 

and html:

<?php   session_start(); include_once 'user.php'; include './templates/header.php';   if (isset($_post['register']) && ($_post['register']) == ($_post["register"])) {                   $user = new user();                 $return = $user->createuser(                     $_post['username'],                     $_post['name'],                     $_post['email'],                     $_post['password'],                     $_post['password2']);          }         if ($return == true) {             echo 'you have registered';         } else {             echo '</br>' . 'sorry, try again';         }      ?> <div class="container">     <div class="jumbotron">         <form method="post" action="">             <label>username: </label><br>             <input name="username" type="text" ><br><br>              <label>name: </label><br>             <input name="name" type="text"><br><br>              <label>email: </label><br>             <input name="email" type="email" ><br><br>              <label>password: </label><br>             <input name="password" type="password" ><br><br><br>              <label>repeat password: </label><br>             <input name="password2" type="password" ><br><br><br>              <input name="register" class="btn btn-primary btn-lg" type="submit" value="register"><br>         </form>     </div> </div> 

please feel free correct me on other mistakes may notice. know there bound some.

i wrote simple example simple , useful

 class validation {          public $currentvalue;         public $values = array();         public $errors = array();          public function __construct() {             parent::__construct();             //   echo "burasi model sayfasi ";           }          public function post($key){             if(isset($_post[$key])){             $this->values[$key]     = $_post[$key];             $this->currentvalue    = $key;             return $this;         }else{ die("hi boo boo ! form values empty");}              }     public function isempty(){         if(empty($this->values[$this->currentvalue])){             $message='the form emppty';             $this->errors[$this->currentvalue]['empty'] =''.$message.'';         }         return $this;     }     public function submit(){         if(empty($this->errors)){             return true;         }else{             return false;         }     }   } 

this example how can use ? firstly need yo call class

$form = new validation ();    $form->post("all need write post name here ") ->isempty(); if($form->submit()){ //everyting ok ! cann add delet or update data  }else{ $data["error"] = $form->errors;  // , sett errorr mesages array can show user errormesages ! done  } }