数据库中有多个斜杠

I have a wordpress based site with an html form that saves data in mysql database through json. I did it in a way like this:

<?php
global $wpdb;
$db = $wpdb->prefix . 'db_table';
$json_query = $wpdb->get_row(
    "
    SELECT app, ts
    FROM $db
    WHERE user_id = $user_id
    ",
    ARRAY_A
);
$json = json_decode($json_query[app], true);
?>

<label>Family Name</label>
<input type="text" name="json[family_name]" <?php echo ($json_ok[family_name] ? 'value="' . $json_ok[family_name] . '"' : ''); ?> />

<?php
$json_send = json_encode( $_POST['json'] );

if (isset($_POST['save'])) {
    $wpdb->update(
        $db,
        array(
            'app'   =>  $json_send
        ),
        array( 'user_id' => $user_id )
    );
?>

It works but if user insert the apostrophe character the sistem save apostrophe preceded by a backslash. Every time user saves, the sistem add a backslash. Now I have the database full of backslashes like this:

{"family_name":"Rossi","indirizzo":"strada d\\\\\\\\\\\\\\\\\\\'oro","first_name":"Maurizio","country_birth":"Italy","city_birth":"Roma"}

How can i solve this? Thanks

I have dealt with the same issue myself when saving and using json encoded stings in wordpress. This is what solved it for me.

Just make a call to stripslashes() when displaying value in input;

like so:

<input type="text" name="json[family_name]" <?php echo (stripslashes($json_ok[family_name]) ? 'value="' . stripslashes($json_ok[family_name]) . '"' : ''); ?> />

When it gets saved again it will stop adding those extra slashes. As mentioned in the comment by John Bell when you make a call to the update function it is calling addslashes().