Argument out of range exception???

I'm stuck with this error. So far my code is functioning properly in terms of retrieving the data but the "argumentoutofrangeexception: argument is out of range Parameter name: index" keep appearing. Any help would be really appreciated.

 public string[] items;
     
     IEnumerator Start () {
         WWW itemsData = new WWW ("http://localhost/Data/sendDataInfo.php");
         yield return itemsData;
         string itemsDataString = itemsData.text;
         items = itemsDataString.Split(';');
         for (int i = 0; i < items.Length ; i++) 
         {
             Debug.Log(GetDataValue(items[i], "condition:"));
         }
 
 
     }
     
     string GetDataValue (string _data, string _index) {
         
         string value = _data.Substring(_data.IndexOf(_index) + _index.Length);
         if (value.Contains ("|")) {
             value = value.Remove (value.IndexOf ("|"));
         }
         return value;
     }