<?php

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

class CreateMentionsPostsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('mentionsPosts', function (Blueprint $table) {
            $table->integer('post_id')->unsigned();
            $table->integer('mentions_id')->unsigned();
            $table->primary(['post_id', 'mentions_id']);
        });
    }

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

<?php

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

class CreateMentionsPostsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('mentions_posts', function (Blueprint $table) {
            $table->integer('post_id')->unsigned();
            $table->integer('mentions_id')->unsigned();
            $table->primary(['post_id', 'mentions_id']);
        });
    }

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

Fix mistake in table name
Fix mistake in table name
