MY_form_validation.php

<?php

class MY_Form_validation extends CI_Form_validation{
    public $ci;
    public function __construct($config = array()){
        parent::__construct($config);
        $this->ci =& get_instance();
    }

    function edit_unique($value, $params) {
        $CI =& get_instance();
        $CI->load->database();
        $CI->form_validation->set_message('edit_unique', "Sorry, that %s is already being used.");
        list($table, $field, $current_id) = explode(".", $params);
        //members.registration_number.$id
        $query = $CI->db->select()->from($table)->where($field, $value)->limit(1)->get();
        if ($query->row() && $query->row()->id != $current_id){
            return FALSE;
        }
    }

    function validate_image($field){
        $CI =& get_instance();
        $check = TRUE;
        if ((!isset($_FILES[$field])) || $_FILES[$field]['size'] == 0) {
            $CI->form_validation->set_message('validate_image', 'The {field} field is required');
            $check = FALSE;
        }else if (isset($_FILES[$field]) && $_FILES[$field]['size'] != 0) {
            $allowedExts = array("gif", "jpeg", "jpg", "png", "JPG", "JPEG", "GIF", "PNG");
            $allowedTypes = array(IMAGETYPE_PNG, IMAGETYPE_JPEG, IMAGETYPE_GIF);
            $extension = pathinfo($_FILES[$field]["name"], PATHINFO_EXTENSION);
            $detectedType = exif_imagetype($_FILES[$field]['tmp_name']);
            $type = $_FILES[$field]['type'];
            if (!in_array($detectedType, $allowedTypes)) {
                $CI->form_validation->set_message('validate_image', 'Invalid Image Content!');
                $check = FALSE;
            }
            if(filesize($_FILES[$field]['tmp_name']) > 2000000) {
                $CI->form_validation->set_message('validate_image', 'The Image file size shoud not exceed 20MB!');
                $check = FALSE;
            }
            if(!in_array($extension, $allowedExts)) {
                $CI->form_validation->set_message('validate_image', "Invalid file extension {$extension}");
                $check = FALSE;
            }
        }
        return $check;
    }

}