Getting undefined variable error when calling a static method.
I'm new to coding. please be kind.
I'm trying to dynamically display an event page. It has $title, $price, $location, etc. with a table in the database titled Onlineevent.
I wanted to add a photo gallery to this event page and thought it would be better to have a new table (event_gallery) with columns (id, event_id, and image_name). The event_id is a foreign key from the  Onlineevent table. 
I'm having no problem calling the Onlineevent data from the database with the method (findy_by_id()). However I cannot call the method that relates to the event_gallery. Please refer to the code.
<?php 
     $event = Onlineevent::find_by_id($_GET['id']); 
    if($event){
    $event_title = $event->event_title;
    $event_type = $event->event_type;
    $event_location = $event->event_location;
    $event_date = $event->event_date;
    $event_start_time = $event->event_start_time; 
    $event_finish_time = $event->event_finish_time; 
    $max_participants = $event->max_participants; 
    $event_price = $event->event_price; 
    $event_description = $event->event_description; 
    $event_picture = $event->picture_path();
    $event_inclusion_1 = $event->inclusion_1;
    $event_inclusion_2 = $event->inclusion_2;
    $event_inclusion_3 = $event->inclusion_3;
    $event_inclusion_4 = $event->inclusion_4;
    $event_inclusion_5 = $event->inclusion_5;
    $event_inclusion_6 = $event->inclusion_6;
    $event_inclusion_7 = $event->inclusion_7;
    $event_inclusion_8 = $event->inclusion_8;
    }
 $images = Eventgallery::find_by_id($_GET['id']);
    if($images){
        $image = $images->picture_path();
    }
            echo $image;
    ?>
Now I'll share the classes.
class Onlineevent extends Db_object{
protected static $db_table = "onlineevent";
protected static $db_table_fields = array('event_type','event_title','event_picture', 'event_location','event_date','event_start_time','event_finish_time','max_participants','event_price','event_description','event_map','inclusion_1','inclusion_2','inclusion_3','inclusion_4','inclusion_5','inclusion_6','inclusion_7','inclusion_8','inclusion_9','inclusion_10');
public $id;
public $event_type;
public $event_title;
public $event_picture;
public $event_location;
public $event_date;
public $event_start_time;
public $event_finish_time;
public $event_koreans;
public $max_participants;
public $event_foreigners;
public $event_price;
public $event_description;
public $event_map;
public $inclusion_1;
public $inclusion_2;
public $inclusion_3;
public $inclusion_4;
public $inclusion_5;
public $inclusion_6;
public $inclusion_7;
public $inclusion_8;
public $inclusion_9;
public $inclusion_10;
public $tmp_path;
public $upload_directory = "images";
public $errors = array();
public $upload_errors_array = array(
0 => 'There is no error, the file uploaded with success',
1 => 'The uploaded file exceeds the upload_max_filesize directive in php.ini',
2 => 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form',
3 => 'The uploaded file was only partially uploaded',
4 => 'No file was uploaded',
6 => 'Missing a temporary folder',
7 => 'Failed to write file to disk.',
8 => 'A PHP extension stopped the file upload.',
);
This is passing $_FILES['uploaded_file'] as an argument
public function set_file($file) {
    if(empty($file) || !$file || !is_array($file)) {
        $this->errors[] = "There was no file uploaded here";
        return false; 
    } elseif($file['error'] !=0){
        $this->error[] = $this->upload_errors_array[$file['error']];
        return false;
    } else {
    $this->event_picture = basename($file['name']);
    $this->tmp_path = $file['tmp_name'];
    $this->type     = $file['type'];
    $this->size     = $file['size'];
    }
}
public function picture_path(){
    return $this->upload_directory.DS.$this->event_picture;
}
public function save(){
    if($this->id){
        $this->update();
    } else {
        if(!empty($this->errors)){
            return false;
        }
        if(empty($this->event_picture) || empty($this->tmp_path)){
            $this->errors[] = "the file was not available";
            return false;
        }
        $target_path = SITE_ROOT .DS. 'admin'.DS. $this->upload_directory. DS . $this->event_picture;
        if(move_uploaded_file($this->tmp_path, $target_path)){
            if($this->create()){
                unset($this->tmp_path);
                return true;
            }
        } else {
            $this->errors[] = "the folder probably does have permission";
            return false; 
        }
    }
}
Here is the second class
<?php
class Eventgallery extends Db_object{
protected static $db_table = "event_gallery";
protected static $db_table_fields = array('event_id','image_name');
public $id;
public $event_id;
public $image_name;
public $tmp_path;
public $upload_directory = "images";
public $errors = array();
//    public $allowTypes = array('jpg','png','jpeg','gif');
public $upload_errors_array = array(
0 => 'There is no error, the file uploaded with success',
1 => 'The uploaded file exceeds the upload_max_filesize directive in php.ini',
2 => 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form',
3 => 'The uploaded file was only partially uploaded',
4 => 'No file was uploaded',
6 => 'Missing a temporary folder',
7 => 'Failed to write file to disk.',
8 => 'A PHP extension stopped the file upload.',
);
This is passing $_FILES['uploaded_file'] as an argument
public function set_file($file) {
    if(empty($file) || !$file || !is_array($file)) {
        $this->errors[] = "There was no file uploaded here";
        return false; 
    } elseif($file['error'] !=0){
        $this->error[] = $this->upload_errors_array[$file['error']];
        return false;
    } else {
    $this->image_name = basename($file['name']);
    $this->tmp_path = $file['tmp_name'];
    $this->type     = $file['type'];
    $this->size     = $file['size'];
    }
}
public function picture_path(){
    return $this->upload_directory.DS.$this->image_name;
}
public function save(){
    if($this->id){
        $this->update();
    } else {
        if(!empty($this->errors)){
            return false;
        }
        if(empty($this->image_name) || empty($this->tmp_path)){
            $this->errors[] = "the file was not available";
            return false;
        }
        $target_path = SITE_ROOT .DS. 'admin'.DS. $this->upload_directory. DS . $this->image_name;
        if(move_uploaded_file($this->tmp_path, $target_path)){
            if($this->create()){
                unset($this->tmp_path);
                return true;
            }
        } else {
            $this->errors[] = "the folder probably does have permission";
            return false; 
        }
    }
}
I would like to be able to call the static function Eventgallery::find_by_id(); so that I can access the data and then print it out on the event page.
Thank you
 
     
    