Update slug value (Laravel)

OffreTableSeeder.php

<?php

use Illuminate\Database\Seeder;

class OffreTableSeeder extends Seeder {
	public function run() {
		$offres = DB::table('offres')->select('id', 'libelle')->get();
		foreach ($offres as $offre) {
			DB::table('offres')
				->where('id', $offre->id)
				->update([
            				'slug' => str_slug($offre->libelle, '-')
            			]);
    		}
    	}
}