Smarty PHP - Create a Function or Plugin/Modifier to Output into JSON

I need a Smarty PHP developer to: A) Create an Action or Function OR a Plugin/Modifier for my smarty php website to output only specific values from database converted into JSON. B) Compare 2 php files and find why my file [login to view URL] made for php5.5 works on my website [apache/php7.2] but [login to view URL] made for php7.2 does not work. Right now on my website i filter items and output their values into json by : {load_bo bo='bo_search' action='search' assign='action_object'} {$action_object->m_list_objects|@json_encode} - but this dumps an array of all of the items' db column values, it's a huge JSON [see example json file attached]. I also can retrieve individual values of items from the loop, example: {foreach name=loop_listings item=list_object from=$action_object->m_list_objects} {$list_object->listing_type} What i need: a PHP Function inside native [login to view URL] file, OR a Modifier like {$action_object->m_list_objects|MODIFIER|@json_encode} that would 1) PRINT ONLY SPECIFIC VALUES INTO JSON (see nodes in attached json file): listing_id, listing_status, title, price, price_status, listing_main_type, listing_type_title, listing_type_id, no_bedrooms, no_bathrooms,no_half_bathrooms, lat, lng, highlight, total_square, board, featured, photo(*), in_wishlist, in_comparelist (*) i believe that main photo is selected from photos array and printed by m_list_objects, if not in photos array we pick listing_photo_file(ONLY 1 photo from Photos array that has "hierarchy": "1",) and the photo's width and height values. 2) OR, if 1) is too complex task, then maybe we could JUST REMOVE PHOTOS JSON node array from the json to reduce it.