Can't Delete Specific Keys and Values from JSON in PHP - php

Question

I'm trying to delete specific key and value pair from external JSON file in PHP when user clicked delete button on the page.
I'm not familiar with PHP so I couldn't able to figure out what I'm doing wrong. I looked at more than 20 questions on stackoverflow but none of them helped to solve my problem.
What I'm trying to achieve in general to write a simple script which user can write something in textbox and submit, show it on the page and when user wants delete it. (I have done the submit and showing part but stuck on deleting part)
Firstly my JSON file:
{
"departman1":
[
{"departman1stage":"John"},
{"departman1stage":"Test"},
{"departman1stage":"Test2"}
]
}
Part of my index.php file:
...
include ('yazdir.php');
include ('sil.php');
<div class='icerik'>
<?php
foreach ($json['departman1'] AS $d){
echo '<p class="' . $d['departman1stage'] .'">';
echo "--> ";
echo $d['departman1stage'];
echo '<form action="sil.php" method="POST"><button type="submit" class="dugme" name="' . $d['departman1stage'] .'"><i class="fa fa-trash"></i></button></form>';
echo "<br>";
echo "</p>";
}
?>
</div>
<br>
<form action="yazdir.php" method="POST">
<div class="icerik"><p><input type="text" name="departman1stage"></p></div>
<br>
<input type="submit" value="Gonder">
</form>
...
It is not related with problem but I still put my yazdir.php code:
$json_sifreli = file_get_contents ("data.json");
$json = json_decode($json_sifreli, true);
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$data = array(
'departman1stage' => $_POST["departman1stage"]
);
array_push ( $json['departman1'], $data );
$json_sifreleme = json_encode($json, true);
file_put_contents('data.json', $json_sifreleme);
}
sil.php is currently blank, as I said I tried different methods. Some of them deleted whole JSON file and put 'null' into it. Some of them deleted unrelated key and value pair. As a last resort, I decided to write here.
Thanks in advance, sorry for taking your time.

Answer 1

You can delete keys using the PHP built-in unset function. It works on individual array keys:
<?php
$foo = [
'a' => 23,
'b' => 42,
];
unset($foo['a']);
var_dump($foo);
Results in:
array(1) {
["b"]=>
int(42)
}
PHP arrays are hash maps, no matter if keys are strings are numeric. In your example JSON, departman1 is an array with numeric keys. You can delete numeric keys with unset as well:
$bar = [
23,
42,
];
unset($bar[0]);
var_dump($bar);
Results in:
array(1) {
[1]=>
int(42)
}
Note that the dump shows 1 as key. Unsetting numeric keys does not cause the array to be renumbered. You end up with holes and this will show up in json_encode output:
echo json_encode($bar);
// Results in: {"1":42}
So you could go through the swamp of using a JSON file as data store, but be cautioned it's a Pandoras Box full of hardships. It also doesn't scale beyond one concurrent user because json_encode and json_decode do not provide ACID properties, which database management systems provide you. My suggestion: ditch the JSON file and pick up a proper database such as PostgreSQL or MySQL (they have good support in PHP via PDO).
view the example code in playground
(BTW: You are using the $_POST variable directly, which is unsafe user input. Sanitizing input can be done with PHP built-in filter_var function.)