PHP: Get id from database, send to other function to get content? - php

Question

I hope the title was descriptive enough, i wasn't sure how to name it.
Let's say i have the following code:
Class Movie_model {
public method getMoviesByDate($date) {
// Connects to db
// Gets movie IDs from a specific date
// Loop through movie IDs
// On each ID, call getMovieById() and store the result in an array
// When all IDs has looped, return array with movies returned from getMovieById().
}
public function getMovieById($id) {
// Get movie by specified ID
// Also get movie genres from another method
// Oh, and it gets movie from another method as well.
}
}
I always want to get the same result when getting a movie (I always want the result from getMovieById().
I hope you get my point. I will have many other functions like getMoviesByDate(), i will also have getMoviesByGenre() for example, and i want that to return the same movie info as getMovieById() as well.
It it "ok" to do it this way? I know this puts more load on the server and increases load time, but is there any other, better way that i don't know of?
EDIT: I clarified the code in getMoviesByDate() a bit. Also, getMovieByDate() is just an example. As i said, i will be calling methods like getMoviesByGenre() also.
EDIT: I'm currently running 48 database queries on the frontpage of my project, and the frontpage is still far from finished, so that number would at least triple when i'm done. Almost all queries take around 0.0002, but as the database keeps growing that number will rise dramatically i'm guessing. I need to change something.

Answer 1

I don't think it's good to work like this in this particular case. The function getMoviesByDate would return an amount of "n" movies (or movie ids) from a single query. For each id in this query you would have a separate query to get the movie by the specified ID.
This would mean if the first function would return 200 movies, you would run the getMovieById() function (and the query inside it) 200 times. A better practice (IMO) would be to just get all the info you require in the getMoviesByDate() function and return it as a collection.

Answer 2

It doesn't seem very logical to have getMoviesByDate() and getMoviesById() methods on a Movie class.
An alternative would be to have some sort of MovieManager class that does all of the retrieving, and returns Movie objects.
class MovieManager {
public function getMoviesByDate($date) {
// get movies by date, build an array of Movie objects and return
}
public function getMoviesByGenre($genre) {
// get movies by genre, build an array of Movie objects and return
}
public function getMovieById($id) {
// get movie by id, return Movie object
}
}
Your Movie class would just have properties and methods specific to a single movie:
class Movie {
public id;
public name;
public releaseDate;
}
It's OK to have separate methods for getting by date, genre etc etc, but you must ensure that you are not calling for the same records multiple times - in that case you will want a single query that could join the various tables you need.
Edit - after you have clarified your question:
The idea of getting movie IDs by date, then running them all through getMovieById() is bad! The movie data should be pulled when getting by date, so you don't have to hit the database again.

Answer 3

You can modified your getMovieById function. You can pass date as a parameter, the function should return the movies by their id and filtered by date.

Answer 4

To keep track which records you've already loaded into RAM previously you can use a base class for your models which saves the id's of the records already loaded and a reference to object the model object in the RAM.
class ModelBase {
/* contains the id of the current record, null if new record */
protected $id;
// keep track of records already loaded
static $loaded_records = Array();
public function __construct(Array $attr_values) {
// assign $attr_values to this classes attributes
// save this instance in class variable to reuse this object
if($attr_values['id'] != null) {
self::$loaded_records[get_called_class()][$attr_values['id']] = $this;
}
}
public static function getConcurrentInstance(Array $attr_values) {
$called_class = get_called_class();
if(isset(self::$loaded_records[$called_class][$attr_values['id']])) {
// this record was already loaded into RAM
$record = self::$loaded_records[$called_class][$attr_values['id']];
// you may need to update certain fields of $record
// from the data in $attr_values, because the data in the RAM may
// be old data.
} else {
// create the model with the given values
$record = new $called_class($attr_values);
}
return $record;
}
// provides basic methods to update records in ram to database etc.
public function save() {
// create query to save this record to database ...
}
}
Your movie model could look something like this.
Class MovieModel extends ModelBase {
// additional attributes
protected $title;
protected $date;
// more attributes ...
public static function getMoviesByDate($date) {
// fetches records from database
// calls getConcurrentInstance() to return an instance of MovieModel() for every record
}
public static function getMovieById($id) {
// fetches record from database
// calls getConcurrentInstance() to return an instance of MovieModel()
}
}
Other things you could do do decrease the load on the DB:
Only connect once to the database per request. There are also possibilities to share a connection to a database between multiple requests.
Index thefields in your database which get searched often.
only fetch the records you need
Prevent to load the same record twice (if it didn't change)