Model_9.4.php

<?php

require_once 'db_connect_model.php';
abstract class Model
{
    /** @var PDO|null Connection to the database */
    protected static $dbc = null;

    /** @var array Database values for a single record. Array keys should be column names in the DB */
    protected $attributes = array();

    /**
     * Constructor
     *
     * An instance of a class derived from Model represents a single record in the database.
     *
     * $param array $attributes Optional array of database values to initialize the model record with
     */
    public function __construct(array $attributes = array())
    {
        self::dbConnect();

        // @TODO: Initialize the $attributes property with the passed value
        $this->attributes = $attributes;
    }

    /**
     * Connect to the DB
     *
     * This method should be called at the beginning of any function that needs to communicate with the database
     */
    protected static function dbConnect()
    {
        if (!self::$dbc) {
            // @TODO: Connect to database
            self::$dbc = new PDO('mysql:host=' . DB_HOST . ';dbname=' . DB_NAME, DB_USER, DB_PASS);

            self::$dbc->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        }
    }

    /**
     * Get a value from attributes based on its name
     *
     * @param string $name key for attributes array
     *
     * @return mixed|null value from the attributes array or null if it is undefined
     */
    public function __get($name)
    {
        // @TODO: Return the value from attributes for $name if it exists, else return null
        if(array_key_exists($name, $this->attributes)){
            return $this->attributes[$name];
        }
        return null;
    }

    /**
     * Set a new value for a key in attributes
     *
     * @param string $name  key for attributes array
     * @param mixed  $value value to be saved in attributes array
     */
    public function __set($name, $value)
    {
        // @TODO: Store name/value pair in attributes array
        $this->attributes[$name] = $value;
    }

    /** Store the object in the database */
    public function save()
    {
        // @TODO: Ensure there are values in the attributes array before attempting to save

        if(empty($this->attributes)){
            throw new InvalidArgumentException('There are no values to insert/update');
        }
        if(isset($this->attributes['id'])){
            $this->update();
        } else{
            $this->insert();
        }
    }
    /**
     * Insert new entry into database
     *
     * NOTE: Because this method is abstract, any child class MUST have it defined.
     */
    protected abstract function insert (); 
    //$query = 'INSERT INTO users(name, email, password) VALUES(:name, :email, :password)';
    /**
     * Update existing entry in database
     *
     * NOTE: Because this method is abstract, any child class MUST have it defined.
     */
    
    protected abstract function update (); 

    protected abstract function delete ();
}