Laravel 5 many-to-many migration table for belongsToMany() connections between two Entities. This is a so called pivot table two foreign keys, that create its index.

create_many_to_many_table.php

<?php

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

class CreateAuthorEntryTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('author_entry', function (Blueprint $table) {
            $table->integer('author_id')->unsigned()->index();
            $table->foreign('author_id')->references('id')
                  ->on('authors')->onDelete('cascade');
      
            $table->integer('entry_id')->unsigned()->index();
            $table->foreign('entry_id')->references('id')
                  ->on('entries')->onDelete('cascade');

            $table->timestamps();
        });
    }

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