PHP saves null to JSON file

Question

I have a problem with my PHP file. I want to save data from my HTML form to external JSON file "data.json". When I fire button to save it it returns message that everything is fine and data is added. Unfortunetaly, when I check my data.json file, it contains null instead of data from a form. Here is my code:

HTML:

 <form class="form form-group" action="save.php" method="POST">
   <label class="control-label" for="focusedInput">Nazwa knajpy</label>
   <input name="name" class="input form-control" id="focusedInput" type="text" value="Wpisz nazwę knajpy">

   <label class="control-label" for="focusedInput">Kategoria knajpy</label>
   <input name="category" class="input form-control" id="focusedInput" type="text" value="Bar/restauracja">

   <label class="control-label" for="focusedInput">Adres</label>
   <input name="addres" class="input form-control" id="focusedInput" type="text" value="Wpisz adres knajpy">

   <label class="control-label" for="focusedInput">Nazwa zdjęcia</label>
   <input name="img" class="input form-control" id="focusedInput" type="text" value="Wpisz nazwę zdjęcia jpg">

   <label class="control-label" for="focusedInput">Cena</label>
   <input name="price" class="input form-control" id="focusedInput" type="text" value="Wpisz cenę piwa">

   <input type="submit" class="btn btn-primary" value="Dodaj knajpę">
  </form>

save.php:

<?php

   $myFile = "data/data.json";
   $arr_data = array(); // create empty array

  try
  {
       //Get form data
       $formdata = array(
          'name'=> $_POST['name'],
          'category'=> $_POST['category'],
          'address'=>$_POST['address'],
          'img'=> $_POST['img'],
          'price'=> $_POST['price']
       );

       //Get data from existing json file
       $jsondata = file_get_contents($myFile);

       // converts json data into array
       $arr_data = json_decode($jsondata, true);

       // Push user data to array
       array_push($arr_data,$formdata);

       //Convert updated array to JSON
       $jsondata = json_encode($arr_data, JSON_PRETTY_PRINT);

       //write json data into data.json file
       if(file_put_contents($myFile, $jsondata)) {
            echo 'Data successfully saved';
        }
       else 
            echo "error";

   }
   catch (Exception $e) {
            echo 'Caught exception: ',  $e->getMessage(), "\n";
   }

?>

Thanks for help!

Start debugging - var_dump all your variables.

u_mulder
– u_mulder

2017-04-02 15:42:39 +00:00
Commented Apr 2, 2017 at 15:42 — u_mulder
– u_mulder, Commented Apr 2, 2017 at 15:42

segFault · Accepted Answer · 2017-04-02 15:45:34Z

3

This line is probably causing issues: $arr_data = json_decode($jsondata, true);

You should make sure it's not empty before you start working with it.

You could add a check like: $arr_data = !empty($jsondata) ? json_decode($jsondata, true) : array();

You may want to perform another check after that as well to make sure you have an array as you expect.

answered Apr 2, 2017 at 15:45

segFault

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