I’ve figured out how to add new field to database using Prestashop (1.4.3, but I think for the newer versions would be the same). This solution gives you new field in database and you will be able to edit / save data to this field in your admin panel, for my example I needed a field which was called “number of photos”. Below you can see how it works.
When you want to get it you should make some improvements. First of all just create a new field in your database it will be called “nb_photos” in my case.
1. Open AdminProducts.php file (/[admin_panel]/tabs/AdminProducts.php) and add this line (line 2194):
<td class="col-left">'.$this->l('Number of photos:').'</td>
<input size="55" type="text" name="nb_photos" value="'.htmlentities($this->getFieldValue($obj, 'nb_photos'), ENT_COMPAT, 'UTF-8').'" style="width: 130px; margin-right: 44px;" />
<span class="hint" name="help_box">'.$this->l('Number of photos') . '</span>
2. Open Product.php (classes/Product.php) and add:
$fields['ean13'] = pSQL($this->ean13);
$fields['nb_photos'] = pSQL($this->nb_photos);
$fields['upc'] = pSQL($this->upc);
And that’s all.
If you need some more information about it just let me know using comments box