Validation of multi-language fields showing error warnings

[ELEGANTAL]

I am new prestashop developer. I have created a module following documentation. I have difficulty understanding one thing. As I understood, multilanguage fields are set to model as array. Like for example:

$model->title[1] = 'English title';

$model->title[2] = 'Spanish title';

 

But when I submit the form and validate my model, I get warnings:

Warning on line 408 in file /var/www/html/prestashop/classes/Validate.php
[2] preg_match() expects parameter 2 to be string, array given

 

If I go to that line in Validate.php it is really taking array of values and using it as single variable. like this:

$model->title = array(1=>'English title', 2=>'Spanish title');

 

If I remove validation rule, it works fine. 

I think I am missing something. Because my module is too big, I cannot post all content here. and I am not sure where the problem is. Any help is appreciated. If anyone had this problem before please let me know the solution.