PHP后期静态绑定问题

Question

<?php
$user = new User();
$user->username = "johnsmith";
$user->password = "555";
$user->first_name = "john";
$user->last_name = "smith";
$user->create();
?>

扩展DatabaseObject类的用户类。..

class User extends DatabaseObject {


    protected static $table_name="users";
    protected static $db_fields = array('id', 'username', 'password', 'first_name', 'last_name');
    public $id;
    public $username;
    public $password;
    public $first_name;
    public $last_name;
 }

带有后期静态绑定的DatabaseObject类。..

class DatabaseObject {

protected static function attributes() {
 $attributes = array();
 foreach(static::$db_fields as $field) {

    if(property_exists(get_called_class(), $field)) {
    $attributes[$field] = get_called_class()->$field;
    }
      }
      return $attributes;
          }

protected static function sanitized_attributes() {
 global $database;
     $clean_attributes = array();
 foreach(self::attributes() as $key => $value) {
    $clean_attributes[$key] = $database->escape_value($value);
      }
      return $clean_attributes;
      }


public static function create() { 
 global $database;

  $attributes = self::sanitized_attributes();
  $sql = "INSERT INTO ".static::$table_name." (";
  $sql .= join(",", array_keys($attributes));
  $sql .=") VALUES ('";
  $sql .= join("', '", array_values($attributes));
  $sql .= "')";

  if($database->query($sql)) { 
   static::$id = $database->insert_id();// get last id saved in database and puts it in the id arguement
   return true;
  } else {
    return false; 
  }

}

Answer 1

如果希望继续使用该结构，应该将静态字段$db_fields设置为DatabaseObject。否则，将DatabaseObject的类型更改为abstract，为数据库fieldset设置一个空数组，并将其设置为Protected。作为DatabaseObject（User）实现的__construct函数的一部分，使用setfields->array(...)来设置映射的字段。或者，您可以允许像$user->foo这样的直接属性调用，并使用__get&_set魔法方法和预定义所有允许的字段，而不是使用映射数组。

下面是用于打印SQL的DatabaseObject类：

class DatabaseObject {
    protected static function attributes() {
        $attributes = array();
            foreach(static::$db_fields as $field) {
                if(property_exists(get_called_class(), $field)) {
                    $attributes[$field] = get_called_class()->$field;
                }
            }
        return $attributes;
    }

    protected static function sanitized_attributes() {
        $clean_attributes = array();
        foreach(self::attributes() as $key => $value) {
            $clean_attributes[$key] = $value;
        }
        return $clean_attributes;
    }

    public static function create() { 
        $attributes = self::sanitized_attributes();
        $sql = "INSERT INTO ".static::$table_name." (";
        $sql .= join(",", array_keys($attributes));
        $sql .=") VALUES ('";
        $sql .= join("', '", array_values($attributes));
        $sql .= "')";

        print $sql;
    }
}

现在，如果我按照您的示例运行它，我会得到以下输出：

php > $user->create();
PHP Notice:  Trying to get property of non-object in php shell code on line 6
PHP Notice:  Trying to get property of non-object in php shell code on line 6
PHP Notice:  Trying to get property of non-object in php shell code on line 6
PHP Notice:  Trying to get property of non-object in php shell code on line 6
PHP Notice:  Trying to get property of non-object in php shell code on line 6
INSERT INTO users (id,username,password,first_name,last_name) VALUES ('', '', '', '', '')

理想情况下，当您使用方法时，它们应该是非静态的，因此对于标准的OOP编程实践，A扩展B，$B是B，$b->foo()html" target="_blank">调用A::foo()，其中foo()是A的非静态方法。

在数据库访问中使用静态绑定有什么原因吗？

编辑--

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