How can i delete object from json file with PHP based on ID

Question

Hi i wonder how i can delete data from json file based on id if my json struct looks like that:

[
    {
        "id": 1,
        "title": "a",
        "decription": "b"
    },
    {
        "id": 2,
        "title": "c",
        "decription": "d"
    }
]

What I've tried so far:

     if (isset($_POST['delete_post'])) 
     {

        $id = $_POST['post-id'];

        if(empty($id)) return;

        $posts = json_decode(file_get_contents('posts.json'));

        foreach ($posts as $post) 
        {
            if ($post->id == $id) 
            {
                unset ($post);
            }
            $save = json_encode($posts, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
            file_put_contents('posts.json', $save);
        }

     }

And i literally stuck at this ponint.

Hi, You need to show some effort / code, then people will help! Maybe try getting it into an array first? — ficuscr
– ficuscr, Commented May 3, 2018 at 20:32
Looks pretty good to me. I'll try it. Are you simply getting some syntax error? Checked logs. Concept is on track. — ficuscr
– ficuscr, Commented May 3, 2018 at 20:38
Nah, not getting any errors, but it simply doesn't delete anything — Hiurako
– Hiurako, Commented May 3, 2018 at 20:40

Tiago Peres · Accepted Answer · 2021-03-22 09:20:18Z

2

unset $post doesn't remove the element from the array, it just unsets that temporary variable.

After unsetting the element you need to use array_values() to get a new array with consecutive indexes. If there's a gap in the indexes, json_encode() will encode it as an object.

You also should break out of the loop once you find the element to delete and rewrite the file.

foreach ($posts as $i => $post) 
{
    if ($post->id == $id) 
    {
        unset ($posts[$i]);
        $save = json_encode(array_values($posts), JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
        file_put_contents('posts.json', $save);
        break;
    }
}

edited Mar 22, 2021 at 9:20

Tiago Peres

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answered May 3, 2018 at 20:41

Barmar

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Comments

bnorb · Accepted Answer · 2018-05-03 20:43:45Z

1

It seems your unset is not working because you don't pass $post it by reference. I would do it with array_filter tho.

function deleteById($json, $id) {
    return json_encode(array_filter(json_decode($json, true), 
        function($e) use ($id) {
          return $e['id'] != $id;
        }
    ));
}

answered May 3, 2018 at 20:43

bnorb

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Comments

Philipp · Accepted Answer · 2018-05-03 20:43:53Z

1

There's and array_filter function in php, which is perfect for your case.

// ...
$posts = array_filter($posts, function($item) use ($id) {
    return $item != $id;
});
// ...

Btw. your code don't work, because you unset only the current loop var and not the actual array item. If you pass an key to the foreach, you could also delete the actual array item.

foreach ($posts as $key => $post) {
    if ($post->id == $id) {
        unset($posts[$key]);
    }
}
// save json

edited May 3, 2018 at 20:43

answered May 3, 2018 at 20:40

Philipp

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