日志含义Laravel 5.0 [PDOException] SQLSTATE[HY000]: General erro

下午好。在laravel 5.0中，我在主机上创建两个表的关系时遇到了一个小问题。

我的产品迁移表:

<?php
use Illuminate'Database'Schema'Blueprint;
use Illuminate'Database'Migrations'Migration;
class CreateProductsTable extends Migration {
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('products', function(Blueprint $table)
        {
            $table->increments('id');
            $table->string('name', 255);
            $table->string('slug');
            $table->text('description');
            $table->string('extract', 300);
            $table->decimal('price', 8, 2);
            $table->string('quantity', 300);
            $table->string('image', 300);       
            $table->boolean('visible');
            $table->integer('category_id')->unsigned();
            $table->foreign('category_id')
                  ->references('id')
                  ->on('categories');
            $table->integer('brand_id')->unsigned();
            $table->foreign('brand_id')
                  ->references('id')
                  ->on('brands');
            $table->timestamps();
        });
    }
    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::drop('products');
    }
}

我的产品型号:

<?php
namespace App;
use Illuminate'Database'Eloquent'Model;
class Product extends Model
{
    protected $table = 'products';
    protected $fillable = ['name', 'slug', 'description', 'extract', 'price', 'quantity', 'image', 'visible', 'category_id', 'brand_id'];

    // Relation with Category
    public function category()
    {
        return $this->belongsTo('App'Category');
    }
    // Relation with Brand
    public function brand()
    {
        return $this->belongsTo('App'Brand');
    }
    /*public function upload()
    {
        return $this->hasOne('App'Upload');
    }*/
    //Query para buscador
    public function scopeName($query, $name)
    {
        //dd("scope: " . $name);
        $query->where('DB::raw("CONCAT(name, '', description, '', price, '', quantity)"), "LIKE", "%$name%");
    }
}

我的类别模型:

<?php
namespace App;
use Illuminate'Database'Eloquent'Model;
class Category extends Model
{
    protected $table = 'categories';
    protected $fillable = ['name'];
    public $timestamps = false;
    //Query para buscador
    public function scopeName($query, $name)
    {
        //dd("scope: " . $name);
        $query->where('DB::raw("CONCAT(name)"), "LIKE", "%$name%");
    }
}

我的品牌模型:

<?php 
namespace App;
use Illuminate'Database'Eloquent'Model;
class Brand extends Model
{
    protected $table = 'brands';
    protected $fillable = ['name'];
    public $timestamps = false;
    public function products()
    {
        return $this->hasMany('App'Product');
    }
    //Query para buscador
    public function scopeName($query, $name)
    {
        //dd("scope: " . $name);
        $query->where('DB::raw("CONCAT(name)"), "LIKE", "%$name%");
    }
}

当我运行迁移时，生成以下错误消息:

Migration table created successfully.

  [Illuminate'Database'QueryException]
  SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL
  : alter table `products` add constraint products_brand_id_foreign foreign k
  ey (`brand_id`) references `brands` (`id`))



  [PDOException]
  SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint

谁能帮我?