Filter MySQLi with checkboxes - php

Question

At the moment, I have a page that is displaying some posts. News posts, blog posts etc. What I want to achieve is having checkboxes so the user can check off, whatever kind of post he/she wants to see.
I should for instance be able to check off ´news´ and ´talking points´ and only see posts with those categories, and not see posts with the category ´blog´ for instance.
My current query looks like this (gets all posts, no matter the category). I believe some jQuery should be involved but I am not sure. How can I connect checkboxes with the query?
Can anyone help me with this?
$sql = "SELECT * FROM articles ORDER BY id DESC";
EDIT
I have tried this, but whenever I use the checkboxes, nothing is shown but I do not get an error?
My code:
<?php
if(isset($_POST['submit'])){//to run PHP script on submit
if(!empty($_POST['check_list'])){
$categories = $_POST['check_list'];
// Loop to store and display values of individual checked checkbox.
foreach($categories as $selected){
echo $selected."</br>";
}
}
}
?>
<br /><br />
<?php
if(!empty($_POST['check_list'])){
$sql = "SELECT * FROM articles ORDER BY id DESC WHERE `category` IN (".implode(',',$categories).")";
} else {
$sql = "SELECT * FROM articles ORDER BY id DESC";
}

Answer 1

Each checkbox should have a value. When you submit your form (probably a $_POST) you will see on the backend which checkboxes are checked. You can inspire from this tutorial: https://www.formget.com/php-checkbox/
IMPORTANT - You should filter the form data before using it in your SQL query. You can inspire from here: http://php.net/manual/en/function.filter-input.php
And you should prepare the variable before using it in the SQL Query:
$unsafe_variable = $_POST["user-input"];
$safe_variable = mysql_real_escape_string($unsafe_variable);
Now that you know which checkboxes are checked, you need to change the SQL query in order to filter by them.
So I suppose the checkboxes values are numbers (representing id's). So you will have an array called $ids that will contain all the checked checkboxes. Your mysql query will become something like:
$sql = "SELECT * FROM articles WHERE `id_category` IN (".implode(',',$ids).") ORDER BY id DESC";