update

app/MedicalCenter.php

@@ -6,9 +6,13 @@ use Illuminate\Database\Eloquent\Model;
 
 class MedicalCenter extends Model
 {
-    public $fillable = ['name'];
+    public $fillable = ['name', 'city_id', 'address', 'phone_number'];
     public function users()
     {
         return $this->hasMany('App\User');
     }
+    public function city()
+    {
+        return $this->belongsTo('App\City');
+    }
 }