Laravel Many to Many Relationship Example

2 years ago admin Laravel

Laravel many to many relationship is a bit more complicated than hasOne and hasMany, a good example of this relationship is a post that has many tags and those tags are also shared by other posts in the application.

In this tutorial, we will create Post Tag many-to-many relationship first, let's create the migrations. 


Create the posts table migration

I assume that you already know how to create Laravel migrations, so let's create a posts table migration

                                                    
                                                                                                                
<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

return new class extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->id();
            $table->string('title');
            $table->text('body');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('posts');
    }
};


Create the tags table migration

Next, let's create the tags table migration.

                                                        
                                                                                                                        
<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

return new class extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('tags', function (Blueprint $table) {
            $table->id();
            $table->string('name');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('tags');
    }
};


Create the post_tag table migration

Next, let's create the post_tag table migration.

                                                        
                                                                                                                        
<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

return new class extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('post_tag', function (Blueprint $table) {
            $table->id();
            $table->foreignId('tag_id')->constrained();
            $table->foreignId('post_id')->constrained();
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('post_tag');
    }
};


Add relationships in models

Next, we define the relationships in the models.

                                                        
                                                                                                                        
//post model

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    use HasFactory;

    public function tags(){
        return $this->belongsToMany(Tag::class);
    }
}

//tag model
<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Tag extends Model
{
    use HasFactory;

    public function posts(){
        return $this->belongsToMany(Post::class);
    }
}


Create and retrieve the data

So to save the tags we use attach or sync and to display the data we use the tags relationship property.

                                                        
                                                                                                                        
    //save the data
    /**
     * Store a newly created resource in storage.
     *
     * @param  \App\Http\Requests\StorePostRequest  $request
     * @return \Illuminate\Http\Response
     */
    public function store(StorePostRequest $request)
    {
        //
        if($request->validated()){
            $data = $request->all();
            $post = Post::create($data);
            //use sync
            $post->tags()->sync($request->tags);
            //or attach
            $post->tags()->attach($request->tags);
            return redirect()->route('posts.index')->with([
                'success' => 'Post added successfully'
            ]);
        }
    }
    //retrieve the data
    @foreach ($post->tags as $tag)
       <span class="badge bg-dark mx-2">
         {{$tag->name}}
       </span>
    @endforeach

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