[php] Automatically deleting related rows in Laravel (Eloquent ORM)

When I delete a row using this syntax:

$user->delete();

Is there a way to attach a callback of sorts, so that it would e.g. do this automatically:

$this->photo()->delete();

Preferably inside the model-class.

Relation in User model:

public function photos()
{
    return $this->hasMany('Photo');
}

Delete record and related:

$user = User::find($id);

// delete related   
$user->photos()->delete();

$user->delete();

You can actually set this up in your migrations:

$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

Source: http://laravel.com/docs/5.1/migrations#foreign-key-constraints

You may also specify the desired action for the "on delete" and "on update" properties of the constraint:

$table->foreign('user_id')
      ->references('id')->on('users')
      ->onDelete('cascade');

To elaborate on the selected answer, if your relationships also have child relationships that must be deleted, you have to retrieve all child relationship records first, then call the delete() method so their delete events are fired properly as well.

You can do this easily with higher order messages.

class User extends Eloquent
{
    /**
     * The "booting" method of the model.
     *
     * @return void
     */
    public static function boot() {
        parent::boot();

        static::deleting(function($user) {
             $user->photos()->get()->each->delete();
        });
    }
}

You can also improve performance by querying only the relationships ID column:

class User extends Eloquent
{
    /**
     * The "booting" method of the model.
     *
     * @return void
     */
    public static function boot() {
        parent::boot();

        static::deleting(function($user) {
             $user->photos()->get(['id'])->each->delete();
        });
    }
}

I would iterate through the collection detaching everything before deleting the object itself.

here's an example:

try {
        $user = User::findOrFail($id);
        if ($user->has('photos')) {
            foreach ($user->photos as $photo) {

                $user->photos()->detach($photo);
            }
        }
        $user->delete();
        return 'User deleted';
    } catch (Exception $e) {
        dd($e);
    }

I know it is not automatic but it is very simple.

Another simple approach would be to provide the model with a method. Like this:

public function detach(){
       try {
            
            if ($this->has('photos')) {
                foreach ($this->photos as $photo) {
    
                    $this->photos()->detach($photo);
                }
            }
           
        } catch (Exception $e) {
            dd($e);
        }
}

Then you can simply call this where you need:

$user->detach();
$user->delete();

You can use this method as an alternative.

What will happen is that we take all the tables associated with the users table and delete the related data using looping

$tables = DB::select("
    SELECT
        TABLE_NAME,
        COLUMN_NAME,
        CONSTRAINT_NAME,
        REFERENCED_TABLE_NAME,
        REFERENCED_COLUMN_NAME
    FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
    WHERE REFERENCED_TABLE_NAME = 'users'
");

foreach($tables as $table){
    $table_name =  $table->TABLE_NAME;
    $column_name = $table->COLUMN_NAME;

    DB::delete("delete from $table_name where $column_name = ?", [$id]);
}

Note: This answer was written for Laravel 3. Thus might or might not works well in more recent version of Laravel.

You can delete all related photos before actually deleting the user.

<?php

class User extends Eloquent
{

    public function photos()
    {
        return $this->has_many('Photo');
    }

    public function delete()
    {
        // delete all related photos 
        $this->photos()->delete();
        // as suggested by Dirk in comment,
        // it's an uglier alternative, but faster
        // Photo::where("user_id", $this->id)->delete()

        // delete the user
        return parent::delete();
    }
}

Hope it helps.

yeah, but as @supersan stated upper in a comment, if you delete() on a QueryBuilder, the model event will not be fired, because we are not loading the model itself, then calling delete() on that model.

The events are fired only if we use the delete function on a Model Instance.

So, this beeing said:

if user->hasMany(post)
and if post->hasMany(tags)

in order to delete the post tags when deleting the user, we would have to iterate over $user->posts and calling $post->delete()

foreach($user->posts as $post) { $post->delete(); } -> this will fire the deleting event on Post

VS

$user->posts()->delete() -> this will not fire the deleting event on post because we do not actually load the Post Model (we only run a SQL like: DELETE * from posts where user_id = $user->id and thus, the Post model is not even loaded)

It is better if you override the delete method for this. That way, you can incorporate DB transactions within the delete method itself. If you use the event way, you will have to cover your call of delete method with a DB transaction every time you call it.

In your User model.

public function delete()
{
    \DB::beginTransaction();

     $this
        ->photo()
        ->delete()
    ;

    $result = parent::delete();

    \DB::commit();

    return $result;
}

As of Laravel 5.2, the documentation states that these kinds of event handlers should be registered in the AppServiceProvider:

<?php
class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        User::deleting(function ($user) {
            $user->photos()->delete();
        });
    }

I even suppose to move them to separate classes instead of closures for better application structure.

Or you can do this if you wanted, just another option:

try {
    DB::connection()->pdo->beginTransaction();

    $photos = Photo::where('user_id', '=', $user_id)->delete(); // Delete all photos for user
    $user = Geofence::where('id', '=', $user_id)->delete(); // Delete users

    DB::connection()->pdo->commit();

}catch(\Laravel\Database\Exception $e) {
    DB::connection()->pdo->rollBack();
    Log::exception($e);
}

Note if you are not using the default laravel db connection then you need to do the following:

DB::connection('connection_name')->pdo->beginTransaction();
DB::connection('connection_name')->pdo->commit();
DB::connection('connection_name')->pdo->rollBack();

There are 3 approaches to solving this:

1. Using Eloquent Events On Model Boot (ref: https://laravel.com/docs/5.7/eloquent#events)

class User extends Eloquent
{
    public static function boot() {
        parent::boot();

        static::deleting(function($user) {
             $user->photos()->delete();
        });
    }
}

2. Using Eloquent Event Observers (ref: https://laravel.com/docs/5.7/eloquent#observers)

In your AppServiceProvider, register the observer like so:

public function boot()
{
    User::observe(UserObserver::class);
}

Next, add an Observer class like so:

class UserObserver
{
    public function deleting(User $user)
    {
         $user->photos()->delete();
    }
}

3. Using Foreign Key Constraints (ref: https://laravel.com/docs/5.7/migrations#foreign-key-constraints)

$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

In my case it was pretty simple because my database tables are InnoDB with foreign keys with Cascade on Delete.

So in this case if your photos table contains a foreign key reference for the user than all you have to do is to delete the hotel and the cleanup will be done by the Data Base, the data base will delete all the photos records from the data base.