<?php
require '../load.php';

function signup($form){
    if( $form['pass']== $form['repass'] ){

    $exists = $userCore->find_mail( filter_project_form() );

    if($exists==''){
        $isCorrect = ($userCore->insert_user( filter_project_form() ));
            if($isCorrect){echo 'correct';}
    }
    else{
        echo "The user exists now";
    }
  }
  else{
    echo 'The passwords must be identical';
  }
}
?>

<?php
//CONFIG
require 'config.php';
require 'constants.php';

//CORE
require 'core/ddbb.php';
require 'core/user.php';
</code>
//CLASS MODEL
require 'model/class_user.php';

//CONTROLLER
require 'controller/controllerUser.php';

//INSTANCIA
$userCore = new User_core();

<?php
class User_core extends DDBB_core{
    function find_mail($form){
       $sql = "SELECT email FROM user WHERE email='".$form['mail']."'";
        return $this->executeSelectQuery($sql);
    }
}