2番目の子クラスで親クラスメソッドを使用できません

Question

私の考えは、親クラスを作成することでした。Db_objectと私は子クラスで使用できるいくつかのメソッドを入れました。私は、最初の子クラスユーザーを作り、すべてのメソッドをテストし、それらはすべてうまくいきましたが、私は他のクラス（写真）クラスで同じメソッドを使用しようとすると、私はcreate()、update() & delete()を使用することはできません。

私はプログラミングが初めてで経験は豊富です。

Db_object（親）：

<?php 
class Db_object 
{ 
    public static function find_all() 
    { 
     return static::find_by_query("SELECT * FROM " . static::$db_table . " "); 
    } 

    public static function find_by_id($user_id) 
    { 
     global $database; 

     $test_array = array(); 

     $the_result_array = static::find_by_query("SELECT * FROM " . static::$db_table . " WHERE id=$user_id LIMIT 1"); 
     return !empty($the_result_array) ? array_shift($the_result_array) : $test_array; 
    } 

    public static function find_by_query($sql) 
    { 
     global $database; 
     $result_set = $database->query($sql); 

     //We created an empty array, so that we can store values in it 
     $the_object_array = array(); 

     /*if($result_set === FALSE) 
     { 
      die("Error: " . mysqli_error()); 
     } 

     if (!empty($result_set)) 
     {*/ 
      // We use while loop to fetch the database table 
      while($row = mysqli_fetch_array($result_set)) 
      { 

       $the_object_array[] = static::instantiation($row); 
      } 
     /*}*/ 
     return $the_object_array; 
    } 

    //instantiation method loops through the databse record & assign those to object properties. 
    public static function instantiation($the_record) 
    { 
     $calling_class = get_called_class(); 
     $the_object = new $calling_class; 

     foreach ($the_record as $the_attribute => $value) 
     { 
      if($the_object->has_the_attribute($the_attribute)) 
      { 
       $the_object->$the_attribute = $value; 
      } 
     } 
     return $the_object; 
    } 

    private function has_the_attribute($the_attribute) 
    { 
     $object_properties = get_object_vars($this); 

     return array_key_exists($the_attribute, $object_properties); 
    } 

    //Method to get all the properties. 
    protected function properties() 
    { 
     $properties = array(); 
     foreach (static::$db_table_fields as $db_field) 
     { 
      if (property_exists($this, $db_field)) 
      { 
       $properties[$db_field] = $this->$db_field; 
      } 
     } 
     return $properties; 
    } 

    //We are looping through protected static $db_table_fields. 
    protected function clean_properties() 
    { 
     global $database; 

     $clean_properties = array(); 

     foreach($this->properties() as $key => $value) 
     { 
      $clean_properties[$key] = $database->escape_string($value); 
     } 
     return $clean_properties; 
    } 

    public function save() 
    { 
     return isset($this->id) ? $this->update() : $this->create(); 
    } 

    public function create() 
    { 
     global $database; 

     $properties = $this->clean_properties(); 

     $sql = "INSERT INTO " . static::$db_table . "(" . implode(",", array_keys($properties)) . ")"; 
     $sql .= "VALUES ('" . implode("','", array_values($properties)) . "')"; 

     if ($database->query($sql)) 
     { 
      //This method is responsible for pulling up the last query, then assigmimg the id to the object. 
      $this->id = $database->the_insert_id(); 
      return true; 
     } 
     else 
     { 
      return false; 
     } 
    } 

    public function update() 
    { 
     global $database; 

     $properties = $this->clean_properties(); 
     $property_pairs = array(); 

     foreach ($properties as $key => $value) 
     { 
      $property_pairs[] = "{$key}='{$value}'"; 
     } 

     $sql = "UPDATE " . static::$db_table . " SET "; 
     $sql .= implode(", ", $property_pairs); 
     $sql .= " WHERE id= " . $database->escape_string($this->id); 

     $database->query($sql); 
     return (mysqli_affected_rows($database->connection) == 1) ? true : false; 
    } 

    public function delete() 
    { 
     global $database; 

     $sql = "DELETE FROM " . static::$db_table . " "; 
     $sql .= "WHERE id=" . $database->escape_string($this->id); 
     $sql .= " LIMIT 1"; 

     $database->query($sql); 
     return (mysqli_affected_rows($database->connection) == 1) ? true : false; 
    } 
} 
?> 

ユーザー（すべてが正常に動作するようです）：

<?php 
include ("init.php"); 

class User extends Db_object 
{ 
    protected static $db_table = "users"; 
    protected static $db_table_fields = array('username', 'password', 'first_name', 'last_name'); 
    public $id; 
    public $username; 
    public $password; 
    public $first_name; 
    public $last_name; 

    public static function verify_user($username, $password) 
    { 
     global $database; 

     //To senatize Username & Password. 
     $username = $database->escape_string($username); 
     $password = $database->escape_string($password); 

     $sql = "SELECT * FROM " . self::$db_table . " WHERE "; 
     $sql .= "username = '{$username}' "; 
     $sql .= "AND password = '{$password}' "; 
     $sql .= "LIMIT 1"; 

     $the_result_array = self::find_by_query($sql); 
     return !empty($the_result_array) ? array_shift($the_result_array) : false; 
    } 
} 
?> 

写真（作成し、ここに私はこれまでやっていることです更新、削除は動作しません）：

<?php 
//include ("init.php"); 

class Photo extends Db_object 
{ 
    protected static $db_table = "photos"; 
    protected static $db_table_fields = array('photo_id', 'title', 'description', 'file_name', 'type', 'size'); 
    public $photo_id; 
    public $title; 
    public $description; 
    public $file_name; 
    public $type; 
    public $size; 


} 
?> 

また、これはquery()メソッドは、データベースクラスから、次のとおりです。

public function query($sql) 
    { 
     $result = mysqli_query($this->connection, $sql); 
     return $result; 
    } 

私はエラーのいずれかの種類を取得できませんでした。コードに混乱がある場合は、私が説明しようとします。

Answer 1

私のコメントに加えて、これらの変更があなたに役立つかどうかを確認してください。なぜクラス内で動的なプロパティを作成しているのか分かりませんが、それはまったく必要ではないと思います。これは、主にクラスをmuddiesし、それが困難に管理することができます：

class DbObject 
    { 
     # Put the base properties in the parent class 
     private static $database; 
     protected $db_table_fields = array(); 
     protected $db_table, 
        $properties; 

     public function __construct() 
     { 
      # Fetch any arguments into the construct 
      $args = func_get_args(); 
      # If a database is passed, assign it 
      if(!empty($args[0]) && is_a($args[0],'mysqli')) 
       self::$database = $args[0]; 
     } 
     # Create a db connection retrieval method 
     public function getDb() 
     { 
      # I use PDO, but I think the instanceof MySQLi is correct... 
      $con = (self::$database instanceof mysqli)? self::$database : false; 
      # If not assigned, throw error 
      if(!$con) 
       throw new Exception('Database is not set.'); 

      return $con; 
     } 
     # I renamed your methods to camel case 
     public function findAll() 
     { 
      if(empty($this->db_table)) 
       throw new Exception('Table name is not set yet.'); 

      return (empty($this->db_table))? false : $this->findByQuery("SELECT * FROM " . $this->db_table . " "); 
     } 
     # Remove static 
     public function findById($user_id) 
     { 
      $test_array = array(); 
      # If you don't bind, at least check it's numeric 
      if(!is_numeric($user_id)) 
       return $test_array(); 

      $the_result_array = $this->findByQuery("SELECT * FROM " . $this->db_table . " WHERE id={$user_id} LIMIT 1"); 
      return !empty($the_result_array) ? array_shift($the_result_array) : $test_array; 
     } 
     # Remove static 
     public function findByQuery($sql) 
     { 
      $database = $this->getDb(); 
      $result_set = $database->query($sql); 
      # We created an empty array, so that we can store values in it 
      $the_object_array = array(); 
      // We use while loop to fetch the database table 
      while($row = mysqli_fetch_assoc($result_set)) { 
       $the_object_array[] = $row; 
      } 
      return $the_object_array; 
     } 
     //Method to get all the properties. 
     protected function properties() 
     { 
      $this->properties = array(); 

      if(empty($this->db_table_fields) || !is_array($this->db_table_fields)) 
       return $this->properties; 

      foreach($this->db_table_fields as $db_field) { 
       if (!isset($this->properties[$db_field])) { 
        $this->properties[$db_field] = $this->db_field; 
       } 
      } 

      return $this->properties; 
     } 

     protected function cleanProperties() 
     { 
      $database = $this->getDb(); 
      $clean_properties = array(); 

      foreach($this->properties() as $key => $value) { 
       $clean_properties[$key] = $database->escape_string($value); 
      } 
      return $clean_properties; 
     } 

     public function save() 
     { 
      return isset($this->id) ? $this->update() : $this->create(); 
     } 

     public function create() 
     { 
      $database = $this->getDb(); 
      $properties = $this->cleanProperties(); 

      $sql = "INSERT INTO " . $this->db_table . "(" . implode(",", array_keys($properties)) . ")"; 
      $sql .= "VALUES ('" . implode("','", array_values($properties)) . "')"; 

      if ($database->query($sql)) { 
       $this->id = $database->the_insert_id(); 
       return true; 
      } 
      else { 
       return false; 
      } 
     } 

     public function update() 
     { 
      $database = $this->getDb(); 
      $properties = $this->cleanProperties(); 
      $property_pairs = array(); 

      foreach ($properties as $key => $value) { 
       $property_pairs[] = "{$key}='{$value}'"; 
      } 

      $sql = "UPDATE " . $this->db_table . " SET "; 
      $sql .= implode(", ", $property_pairs); 
      $sql .= " WHERE id= " . $database->escape_string($this->id); 

      $database->query($sql); 
      return (mysqli_affected_rows($database->connection) == 1) ? true : false; 
     } 

     public function delete() 
     { 
      $database = $this->getDb(); 
      $sql = "DELETE FROM " . $this->db_table . " "; 
      $sql .= "WHERE id=" . $database->escape_string($this->id); 
      $sql .= " LIMIT 1"; 
      $database->query($sql); 
      return (mysqli_affected_rows($database->connection) == 1); 
     } 

     public function getTableFields() 
     { 
      return $this->db_table_fields; 
     } 

     public function describe() 
     { 
      return $this->findByQuery("describe ".$this->db_table); 
     } 
    } 


class User extends DbObject 
    { 
     protected $db_table = "users"; 
     protected $db_table_fields = array('username', 'password', 'first_name', 'last_name'); 
     private $id, 
       $username, 
       $password, 
       $first_name, 
       $last_name; 

     public function verifyUser($username, $password) 
     { 
      try { 
       $database = $this->getDb(); 
       //To senatize Username & Password. 
       $username = $database->escape_string($username); 
       $password = $database->escape_string($password); 

       $sql = "SELECT * FROM " . $this->db_table . " WHERE "; 
       $sql .= "username = '{$username}' "; 
       $sql .= "AND password = '{$password}' "; 
       $sql .= "LIMIT 1"; 

       $the_result_array = $this->findByQuery($sql); 
      } 
      catch (Exception $e) { 
       trigger_error($e->getMessage(),E_USER_NOTICE); 
      } 

      return !empty($the_result_array) ? array_shift($the_result_array) : false; 
     } 
    } 

class Photo extends DbObject 
    { 
     protected $db_table = "photos"; 
     protected $db_table_fields = array('photo_id', 'title', 'description', 'file_name', 'type', 'size'); 
     private $photo_id, 
       $title, 
       $description, 
       $file_name, 
       $type, 
       $size; 
    } 

使用するには：

# Create the database connection 
$MySql = new MySQLi('localhost','username','password','dbname'); 
# Create instance of User pass database 
$User = new User($MySql); 
# Create instance of Photo. Since db is static, you don't have pass database 
# into subsequent extended classes 
$Photo = new Photo(); 
# Describe user table 
print_r($User->describe()); 
# Describe photos table 
print_r($Photo->describe());