PHP writes null to JSON file

Question

I've seen similar posts to this question but I can't seem to figure it out. I have a small PHP script that reads and writes form input to a JSON file, like this –

  $file = 'data.json';

  $arr_data = array();

  $formdata = array(
        'name' => strip_tags( trim($_POST['formName']) ),
        'email' => $email,
        'phone' => strip_tags( trim($_POST['formPhone']) ),
        'message' => strip_tags( trim($_POST['formMessage']) )
        // also tested this just using reg strings
  );

  $jsondata = file_get_contents($file);

  //var_dump($jsondata); returns whatever string content is in the file, so seems to work

  $arr_data = json_decode($jsondata, true);

  array_push($arr_data, $formdata);

  //var_dump($arr_data); returns NULL, not sure what happens here

  $jsondata = json_encode($arr_data, JSON_PRETTY_PRINT);

  file_put_contents($file, $jsondata);

Any ideas? Using PHP 5.5.9, checked that files are writeable. Both files have UTF8 encoding.

Try using var_dump($arr_data) immediately after $arr_data = json_decode($jsondata, true). Also, make sure you can see any errors. Place this at the top of your script ~ error_reporting(E_ALL); ini_set('display_errors', 'On'); — Phil
– Phil, Commented Sep 26, 2017 at 3:58
My data.json file is just blank. Should there be some pretext content in order for it to work? — Staffan Estberg
– Staffan Estberg, Commented Sep 26, 2017 at 3:59
yes, incase it's blank, make $arr_data = array() or preset the json file to [] — Manuel Otto
– Manuel Otto, Commented Sep 26, 2017 at 3:59
instead of array_push() use array_merge() function to append one array to another without comparing their keys. — mith
– mith, Commented Sep 26, 2017 at 4:01

Phil · Accepted Answer · 2017-09-26 04:01:11Z

1

json_decode() will return NULL if the input is blank. Try this to ensure your $arr_data is an array...

$arr_data = json_decode($jsondata, true);
if ($arr_data === null) {
    $arr_data = [];
}

answered Sep 26, 2017 at 4:01

Phil

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1 Comment

Staffan Estberg Over a year ago

Wonderful! That did it :) And always good to learn something new.

Carson · Accepted Answer · 2017-09-26 04:11:57Z

maybe you want this code

<?php
  $file = 'data.json';
  $email='your mail info';
  $arr_data = array();

  $formdata = array(
        'name' => strip_tags( trim($_POST['formName']) ),
        'email' => $email,
        'phone' => strip_tags( trim($_POST['formPhone']) ),
        'message' => strip_tags( trim($_POST['formMessage']) )
        // also tested this just using reg strings
  );

  $jsondata = file_get_contents($file);

  //var_dump($jsondata); returns whatever string content is in the file, so seems to work

  $arr_data = json_decode($jsondata, true);

  // I added for if data.json is null to empty array
  $arr_data = is_null($arr_data)?array():$arr_data;

  array_push($arr_data, $formdata);

  //var_dump($arr_data); returns NULL, not sure what happens here

  $jsondata = json_encode($arr_data, JSON_PRETTY_PRINT);

  file_put_contents($file, $jsondata);
?>

others

you should change your code to keep post data not null or default values and pay attention to file_get_contents method about file length

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