mysql to json

 header('Content-Type: application/json');

    //get the data from table ‘books’
    $query = "SELECT * FROM NOMETABELLA";

    //execute the query
    $result = mysqli_query($link, $query);

    if(!$result){
        echo "Couldn't execute the query";
        die();
    }
    else{
         //creates an empty array to hold data
         $data = array();
          while($row = mysqli_fetch_assoc($result)){
            $data[]=$row;
          }
        //  echo json_encode($data, JSON_PRETTY_PRINT);
        //it will create file results.json with writing mode.
        //you can read more about file handling in PHP here.
        $fp = fopen('NOMEFILE.json', 'w');
        //json_enconde($array, $options(optional) is the method to convert array into JSON
        fwrite($fp, json_encode($data, JSON_PRETTY_PRINT));
        //close the file
        fclose($fp);
    }