using codeigniter PHP Fatal error: Class 'MY_Model' not found

Question

Now I am learning CodeIgniter_2.1.4 but I got a php error;

I have a my_model.php file in /data/www/application/core

<?php

class MY_Model extends CI_Model {
   const DB_TABLE = 'abstract';
   const DB_TABLE_PK = 'abstract';

   private function insert() {
      $this->db->insert($this::DB_TABLE, $this);
      $this->{$this::DB_TABLE_PK} = $this->db->insert_id();
   }

   private function update() {
      $this->db->update($this::DB_TABLE, $this, $this::DB_TABLE_PK);
   }

   public function populate($row) {
      foreach($row as $key => $value) {
         $this->$key = $value;
      }
   }

   public function load($id) {
      $query = $this->db->get_where($this::DB_TABLE, array(
         $this::DB_TABLE_PK => $id,
      ));
      $this->populate($query->row());
   }

   public function delete(){
      $this->db->delete($this::DB_TABLE, array(
         $this::DB_TABLE_PK => $this->{$this::DB_TABLE_PK},
      ));
      unset($this->{$this::DB_TABLE_PK});
   }

   public function save(){
      if(isset($this->{$this::DB_TABLE_PK})) {
         $this->update();
      }
      else {
         $this->insert();
      }
   }

 public function get($limit = 0, $offset = 0) {
      if($limit) {
          $query = $this->db->get($this::DB_TABE, $limit, $offset);
      }
      else {
          $query = $this->db->get($this::DB_TABLE);
      }

      $ret_val = array();
      $class = get_class($this);
      foreach ($query->result() as $row) {
          $model = new $class;
          $model->populate($row);
          $ret_val[$row->{$this::DB_TABLE_PK}] = $model;
      }
      return $ret_val;
   }
}

and my domain model is :

<?php

class Publication extends MY_Model {

    const DB_TABLE = 'publications';
    const DB_TABLE_PK = 'publication_id';

    public $publication_id;
    public $publication_name;

}

well when I get model in my controller I got this php error:

PHP Fatal error:  Class 'MY_Model' not found in /data/www/application/models/publication.php on line 3

I have tried two hours finding the reason but failed ):

Solution

I have a my_model.php file in /data/www/application/core

the my_model.php should be renamed to MY_Model.php.

It should be a case-sensitivity issue. Class names must have the first letter capitalized with the rest of the name lowercase.

Comments

[Felix]

After I add require,I got this error ):Message: require_once(my_model.php): failed to open stream: No such file or directory

[Hashem Qolami]

@Felix Are you developing on Windows? File names are case sensitive on Unix-based operation systems, but not on windows.

[Dave]

where is the my_model file located in relationship to the publication model?

[Hashem Qolami]

@Felix, That's weird, because Windows or Mac servers treat file names as case-insensitive while Linux/Unix does as case-sensitive. If you don't have any case-sensitivity issue on CentOS, that's new to me.

[Hashem Qolami]

CodeIgniter loads all MY_* classes placed in application/core/ automatically. but the point is the classe names and files SHOULD start with MY_ prefix (actually it is configurable) and follow by a Capitalized name.