Many-to-Many Relationships & Pivot Tables

Many-to-Many

// Migration for pivot table
Schema::create('post_tag', function (Blueprint $table) {
    $table->foreignId('post_id')->constrained()->cascadeOnDelete();
    $table->foreignId('tag_id')->constrained()->cascadeOnDelete();
    $table->primary(['post_id', 'tag_id']);
});

// Post model
class Post extends Model
{
    public function tags(): BelongsToMany
    {
        return $this->belongsToMany(Tag::class);
    }
}

// Usage
$tags = Post::find(1)->tags;             // Collection of tags
$posts = Tag::find(1)->posts;            // Collection of posts

// Attach, detach, sync
$post->tags()->attach([1, 2, 3]);        // Add tags
$post->tags()->detach([2]);              // Remove tag
$post->tags()->sync([1, 3, 5]);          // Set exactly these tags
$post->tags()->toggle([2, 4]);           // Toggle tags on/off

// Pivot table with extra columns
return $this->belongsToMany(Tag::class)->withPivot('order')->withTimestamps();
$tag->pivot->order; // Access pivot data

Industry Best Practices

• Always write tests for this functionality - it's the most reliable way to catch regressions when you refactor or update packages
• Document your implementation decisions in code comments, especially when you deviate from Laravel conventions - future team members (including yourself) will thank you
• Follow the single responsibility principle: each class does one thing. If a method grows beyond 20 lines, consider extracting helper methods or moving logic to a service class
• Profile performance with Laravel Debugbar (composer require barryvdh/laravel-debugbar) during development - it shows query counts, memory usage, and timeline for every request
• Keep dependencies up to date: run composer audit regularly to check for security vulnerabilities in your package dependencies

Industry Best Practices

• Always write tests for this functionality - it's the most reliable way to catch regressions when you refactor or update packages
• Document your implementation decisions in code comments, especially when you deviate from Laravel conventions - future team members (including yourself) will thank you
• Follow the single responsibility principle: each class does one thing. If a method grows beyond 20 lines, consider extracting helper methods or moving logic to a service class
• Profile performance with Laravel Debugbar (composer require barryvdh/laravel-debugbar) during development - it shows query counts, memory usage, and timeline for every request
• Keep dependencies up to date: run composer audit regularly to check for security vulnerabilities in your package dependencies

Industry Best Practices

• Always write tests for this functionality - it's the most reliable way to catch regressions when you refactor or update packages
• Document your implementation decisions in code comments, especially when you deviate from Laravel conventions - future team members (including yourself) will thank you
• Follow the single responsibility principle: each class does one thing. If a method grows beyond 20 lines, consider extracting helper methods or moving logic to a service class
• Profile performance with Laravel Debugbar (composer require barryvdh/laravel-debugbar) during development - it shows query counts, memory usage, and timeline for every request
• Keep dependencies up to date: run composer audit regularly to check for security vulnerabilities in your package dependencies

Tip

Practice Task

Quick Quiz

Common Mistake