Creating an Entity Class

Yo guys! Time to level-up our project in a big way. I mean, big. This series is all about an incredible library called Dog-trine. Wait, that's not right - it's Doctrine. But anyways, Doctrine is kinda like a dog: a dog fetches a bone, Doctrine fetches data from the database. But Doctrine does not pee in the house. That's part of what makes it awesome.

But back up: is Doctrine part of Symfony? Nope. Symfony doesn't care how or if you talk to a database at all. You could use a direct PDO connection, use Doctrine, or do something else entirely. As usual, you're in control.

If you want to code along - which you should - then download the code from the screencast page and move into the directory called start. I already have the start code downloaded, so I'll go straight to opening up a new terminal and starting the built-in sever with:

./bin/console server:run

Tip

You may also need to run composer install and a few other tasks. Check the README in the download for those details.

Perfect!

Doctrine is an ORM

Doctrine is an ORM: object relational mapper. In short, that means that every table - like genus - will have a corresponding PHP class that we will create. When you query the genus table, Doctrine will give you a Genus object. Every property in the class maps to a column in the table. Keep this simple idea in mind as we go along: this mapping between a table and a PHP class is Doctrine's main goal.

Oh, and before we hop in, I want you to remember something very important: all the tools in Symfony are optional, including Doctrine. If Doctrine - or any tool - does more harm than good while solving a problem, skip it and do something simpler. Tools are meant to serve you, not the other way around.

Your First Entity Class

Our sweet app displays information about different ocean-living genuses... but so far, all that info is hardcoded. That's so sad.

Instead, let's create a genus table in the database and load all of this dynamically from there. How do you create a database table with Doctrine? You don't! Your job is to create a class, then Doctrine will create the table based on that class. It's pretty sweet. Oh, and the whole setup is going to take about 2 minutes and 25 lines of code. Watch.

Create an Entity directory in AppBundle and then create a normal class inside called Genus:

            
            8 lines
            
            src/AppBundle/Entity/Genus.php
        
                                                    ... lines 1 - 2
                            
            namespace AppBundle\Entity;
            
            class Genus
            
            {
            
            }

You're going to hear this word - entity - a lot with Doctrine. Entity - it sounds like an alien parasite. Fortunately, it's less scary than that: an entity is just a class that Doctrine will map to a database table.

Configuration with... Annotations!

To do that - Doctrine needs to know two things: what the table should be called and what columns it needs. To help it out, we're going to use... drumroll... annotations! Remember, whenever you use an annotation, you need a use statement for it. This will look weird, but add a use for a Column class and let it auto-complete from Doctrine\ORM\Mapping. Remove the Column part and add as ORM:

            
            15 lines
            
            src/AppBundle/Entity/Genus.php
        
                                                    ... lines 1 - 2
                            
            namespace AppBundle\Entity;
            
            use Doctrine\ORM\Mapping as ORM;
            
                                                    ... lines 6 - 15

Tip

You can also configure Doctrine with YAML, XML or PHP, instead of annotations. Check Add Mapping Information to see how to configure it.

Every entity class will have that same use statement. Next, put your cursor inside the class and open up the "Code"->"Generate" menu - cmd+N on a Mac. Ooh, one of the options is ORM Class. Click that... and boom! It adds two annotations - @ORM\Entity and @ORM\Table above the class:

            
            15 lines
            
            src/AppBundle/Entity/Genus.php
        
                                                    ... lines 1 - 6
                            
            /**
            
             * @ORM\Entity
            
             * @ORM\Table(name="genus")
            
             */
            
            class Genus
            
            {
            
            }

Doctrine now knows this class should map to a table called genus.

Configuring the Columns

But that table won't have any columns yet. Lame. Add two properties to get us rolling: id and name. To tell Doctrine that these should map to columns, open up the "Code"->"Generate" menu again - or cmd+N. This time, select ORM Annotation and highlight both properties. And, boom again!

            
            25 lines
            
            src/AppBundle/Entity/Genus.php
        
                                                    ... lines 1 - 6
                            
            /**
            
             * @ORM\Entity
            
             * @ORM\Table(name="genus")
            
             */
            
            class Genus
            
            {
            
                /**
            
                 * @ORM\Id
            
                 * @ORM\GeneratedValue(strategy="AUTO")
            
                 * @ORM\Column(type="integer")
            
                 */
            
                private $id;
            
                /**
            
                 * @ORM\Column(type="string")
            
                 */
            
                private $name;
            
            }

Now we have annotations above each property. The id columns is special - it will almost always look exactly like this: it basically says that id is the primary key.

After that, you'll have whatever other columns you need. Hey, look at the type option that's set to string. That's a Doctrine "type", and it will map to a varchar in MySQL. There are other Doctrine types for strings, floats and text - we'll talk about those soon!

And with just 25 lines of code, we're done! In a second, we'll ask Doctrine to create the genus table for us and we'll be ready to start saving stuff. Well, let's get to it!

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Symfony 3: Doctrine & the Database