reconstruction of the project

app/Models/AdminNotificationSubject.php

@@ -7,10 +7,7 @@ use App\Models\BaseModel;
 class AdminNotificationSubject extends BaseModel
 {
     protected $table = 'admin_notification_subjects';
-    protected $primaryKey = 'id';
-    public $timestamps = true;
-    const CREATED_AT = 'created_at';
-    const UPDATED_AT = 'updated_at';
+
     protected $fillable = [
         'admin_id',
         'subject',
@@ -18,8 +15,15 @@ class AdminNotificationSubject extends BaseModel
         'updated_at',
     ];
 
+    // CI uses created_at / updated_at
+    public $timestamps = true;   
+    protected $casts = [
+        'admin_id' => 'integer',
+    ];
+
+    // Optional relationship (if your admins are in users table)
     public function admin()
     {
         return $this->belongsTo(User::class, 'admin_id');
     }
-}
+}