Null value written to JSON file with PHP - php

Question

EDITED
Problem - A null value is written to the JSON file after the function runs.
Expectation - Capture data entered into HTML form, append it to an existing JSON file.
Some of the Stack resources I've used:
How do I extract data from JSON with PHP?
How to loop through JSON array using PHP
how to write a json file as a datasource in php?
How to Append JSON File in PHP?
How to add to json array in .json file with php
How can I write data in local JSON file using jQuery?
My JSON file looks like this:
{
"records": [
{"Date":"05/04/2016","Miles":168081,"Gallons":11.003,"Cost":28.60,"MPG":24.1,"Street":"5500 Mirage St","City":"Yorba Linda","State":"CA","Zip":92807,"Time":"07:04"},
{"Date":"04/18/2016","Miles":167815,"Gallons":10.897,"Cost":27.23,"MPG":25.7,"Street":"5500 Mirage St","City":"Yorba Linda","State":"CA","Zip":92807,"Time":"15:46"}
],
"error" : false,
"status" : 200
}
EDITED - My PHP script looks like this (update implements Chay's code):
<?php
function runMyFunction() {
// #####
if ($_SERVER['REQUEST_METHOD'] !== 'POST' && !isset($_POST)) { //You may add $_POST[post_name] for validation
die('I need post method!');
}
// check if file exists
$filename = 'mpg-data-file2.json';
if ( ! file_exists($filename) ) {
echo 'ERROR:' . $filename . ' not found' . '<BR>';
} else {
echo 'OK: ' . $filename . ' exists.' . '<BR>';
$data = array(
"Date"=> $_POST['mpg_date'],
"Miles"=> $_POST['mpg_miles'],
"Gallons"=> $_POST['mpg_gallons'],
"Cost"=> $_POST['mpg_cost'],
"MPG"=> $_POST['mpg_mpg'],
"Street"=> $_POST['mpg_street'],
"City"=> $_POST["mpg_city"],
"State"=> $_POST['mpg_state'],
"Zip"=> $_POST['mpg_zip'],
"Time"=> $_POST['mpg_time']
);
//Load data from json file
$dataFile = file_get_contents("mpg-data-file2.json");
$dataFile = json_decode($str_data,true);
//Merge data from post with data from file
$formattedData = array_merge($dataFile['records'],$data);
$formattedData = json_encode($formattedData);
//If data from file is empty, just use data from post
if (empty($dataFile)) {
$formattedData = json_encode($data);
}
//Set a parent key
$records['records'] = $formattedData;
//Overwites everything
/* $handle = fopen($filename,'a+');
fwrite($handle,$records);
fclose($handle); */
file_put_contents($filename,$records, FILE_APPEND | LOCK_EX);
print_r($formattedData);
echo 'OK: ' . '<BR>' . $records . '<BR>';
}
// #####
}//end runMyFunction
/*
if (isset($_GET['hello'])) {
runMyFunction();
} */
if(isset($_POST['mpg_date'],$_POST['mpg_date'],$_POST['mpg_miles'],$_POST['mpg_gallons'],$_POST['mpg_cost'],$_POST['mpg_mpg'],$_POST['mpg_street'],$_POST["mpg_city"],$_POST['mpg_state'],$_POST['mpg_zip'],$_POST['mpg_time'])) {
runMyFunction($_POST);
}
?>
An excerpt of the HTML form looks like this:
<form action="_process.php" method="POST" role="form">
<div class="form-group">
<label for="mpg_date">Fuel Date:</label>
<input type="text" class="form-control" id="mpg_date" name="mpg_date" placeholder="04/18/2016">
</div>
<div class="form-group">
<label for="mpg_miles">Odometer (Miles):</label>
<input type="number" min=”0″ step="any" class="form-control" id="mpg_miles" name="mpg_miles" placeholder="167815">
</div>
<!-- And so on... -->
<div>
<a href='_process.php?hello=true'>Run PHP Function</a>
</div>
</form>

Answer 1

I'm sure that your submission doesn't POST something since you're using anchor (without any javascript) to submit. In the other word, notice I change it to <button>.
<form action="_process.php" method="POST" role="form">
<div class="form-group">
<label for="mpg_date">Fuel Date:</label>
<input type="text" class="form-control" id="mpg_date" name="mpg_date" placeholder="04/18/2016">
</div>
<div class="form-group">
<label for="mpg_miles">Odometer (Miles):</label>
<input type="number" min=”0″ step="any" class="form-control" id="mpg_miles" name="mpg_num" placeholder="167815">
</div>
<!-- And so on... -->
<div>
<button type="submit" role="button">Run PHP Function</button>
</div>
</form>
If you also noticed I also changed the second input name above to mpg_num. And this should be your backend looks.
...
...
if(isset($_POST['mpg_date'], $_POST['mpg_num'])) {
runMyFunction($_POST);
}
Updated
if ($_SERVER['REQUEST_METHOD'] !== 'POST' && !isset($_POST)) { //You may add $_POST[post_name] for validation
die('I need post method!');
}
// check if file exists
$filename = 'mpg-data-file.json';
if ( ! file_exists($filename) ) {
echo 'ERROR:' . $filename . ' not found' . '<BR>';
} else {
echo 'OK: ' . $filename . ' exists.' . '<BR>';
$data = array(
"Date"=> $_POST['mpg_date'],
"Miles"=> $_POST['mpg_miles'],
"Gallons"=> $_POST['mpg_gallons'],
"Cost"=> $_POST['mpg_cost'],
"MPG"=> $_POST['mpg_mpg'],
"Street"=> $_POST['mpg_street'],
"City"=> $_POST["mpg_city"],
"State"=> $_POST['mpg_state'],
"Zip"=> $_POST['mpg_zip'],
"Time"=> $_POST['mpg_time']
);
//Load data from json file
$dataFile = file_get_contents("mpg-data-file.json");
$dataFile = json_decode($str_data,true);
//Merge data from post with data from file
$formattedData = array_merge($dataFile['records'],$data);
//If data from file is empty, just use data from post
if (empty($dataFile)) {
$formattedData = $data;
}
//Set a parent key
$records['records'] = $formattedData;
$records['error'] = false;
$records['status'] = 200;
$records = json_encode($records);
//Overwites everything
$handle = fopen($filename,'w+');
fwrite($handle,$records);
fclose($handle);
print_r($records);
}
I hope this won't consume your environment RAM alot :)

Answer 2

This:
<a href='_process.php?hello=true'>Run PHP Function</a>
will actually submit your form. When you just link to the script that way rather than submitting the form, none of the $_POST values will be set.
It looks like your form just needs a submit button. You can put '_process.php?hello=true' into the form action if you want the if (isset($_GET['hello'])) { check to work.
In other words:
<form action="_process.php?hello=true" method="POST" role="form">
<!-- All your inputs, etc. ...-->
<input type="submit" value="Run PHP Function">
</form>
In order to append the new data to your existing JSON, you'll need to change the order that things happen in your function. The else part should be like this:
// First get the existing JSON from the file and decode it
$str_data = file_get_contents("mpg-data-file.json"); // Get the JSON string
$data = json_decode($str_data,true);// json_decode expects the JSON data, not a file name
// Then create a new data array from the $_POST data and add it to the 'records' key
$new_data = array(
"Date"=> $_POST['mpg_date'],
"Miles"=> $_POST['mpg_miles'],
"Gallons"=> $_POST['mpg_gallons'],
"Cost"=> $_POST['mpg_cost'],
"MPG"=> $_POST['mpg_mpg'],
"Street"=> $_POST['mpg_street'],
"City"=> $_POST["mpg_city"],
"State"=> $_POST['mpg_state'],
"Zip"=> $_POST['mpg_zip'],
"Time"=> $_POST['mpg_time']
);
$data['records'][] = $new_data;
// Then re-encode the JSON and write it to the file
$formattedData = json_encode($data);//format the data
$handle = fopen($filename,'w+');//open or create the file
fwrite($handle,$formattedData);//write the data into the file
fclose($handle);//close the file
print_r($data);