laravelの移行時にエラーが発生しました[PDOException] SQLSTATE [HY000]：一般エラー：1215外部キーを追加できません

An Error Occurred When Laravel Migrate Sqlstate

外部キーを追加したい場所にメソッドを追加する- > unsigned（） OK。

public function up() { Schema::create('posts', function (Blueprint $table) { $table->increments('id') $table->string('flag') $table->string('title') $table->integer('category_id')->unsigned() $table->integer('user_id')->unsigned() $table->text('content') $table->text('markdown') $table->integer('views') $table->integer('comments') $table->timestamp('deleted_at') $table->timestamps() $table->foreign('category_id')->references('id')->on('categories') $table->foreign('user_id')->references('id')->on('users') }) }