Schema::enableForeignKeyConstraints PHP Method

        public static function enableForeignKeyConstraints()
        {
            //Method inherited from \Illuminate\Database\Schema\Builder
            return \Illuminate\Database\Schema\MySqlBuilder::enableForeignKeyConstraints();
        }

 /**
  * Run the migrations.
  *
  * @return void
  */
 public function up()
 {
     Schema::disableForeignKeyConstraints();
     // Add foreign key to contacts table
     Schema::table('contacts', function ($table) {
         $table->foreign('location_id')->references('id')->on('locations');
     });
     // Add foreign keys to gendata table
     Schema::table('gendata', function ($table) {
         $table->foreign('survey_id')->references('id')->on('testdates');
         $table->foreign('tube_id')->references('id')->on('tubes');
     });
     // Add foreign keys to machines table
     Schema::table('machines', function ($table) {
         $table->foreign('modality_id')->references('id')->on('modalities');
         $table->foreign('manufacturer_id')->references('id')->on('manufacturers');
         $table->foreign('location_id')->references('id')->on('locations');
     });
     // Add foreign keys to opnotes table
     Schema::table('opnotes', function ($table) {
         $table->foreign('machine_id')->references('id')->on('machines');
     });
     // Add foreign keys to recommendations table
     Schema::table('recommendations', function ($table) {
         $table->foreign('survey_id')->references('id')->on('testdates');
     });
     // Add foreign keys to testdates table
     Schema::table('testdates', function ($table) {
         $table->foreign('machine_id')->references('id')->on('machines');
         $table->foreign('tester1_id')->references('id')->on('testers');
         $table->foreign('tester2_id')->references('id')->on('testers');
         $table->foreign('type_id')->references('id')->on('testtypes');
     });
     // Add foreign keys to tubes table
     Schema::table('tubes', function ($table) {
         $table->foreign('machine_id')->references('id')->on('machines');
         $table->foreign('housing_manuf_id')->references('id')->on('manufacturers');
         $table->foreign('insert_manuf_id')->references('id')->on('manufacturers');
     });
     Schema::enableForeignKeyConstraints();
 }