Returning search results based off checkboxes
Applying YCS's tutorial can't be dumbed down any further, so I suppose I'll write it out.

if (isset($_POST["action"])) {
    $query = "SELECT link FROM allpostdata WHERE sts = '1'";

    if (!empty($_POST["cate"])) {
        $query .= " AND sca IN (" . str_repeat("?,", count($_POST["cate"]) - 1) . "?)";
    } else {
        $_POST["cate"] = []; // in case it is not set 
    }

    $stmt = $conn-&gt;prepare($query);
    $stmt-&gt;execute($_POST["cate"]);
    $result = $stmt-&gt;fetchAll();
    if (!$result) {
        exit('&lt;h3&gt;No Data Found&lt;/h3&gt;');
    }
    foreach ($result as $row) {
        echo "&lt;a href=\"/single_view.php?p={$row['link']}\"&gt;{$row['link']}&lt;/a&gt;";
    }
}


I assume this will display your links side by side.  You may want to style them a bit to position the links in a user friendly fashion.

Additionally, $('.filter_data'); is doing nothing and can be removed.

I'd probably change the filter_data() declaration to something more brief:

function filter_data() {
    $.post(
       "fetch.php",
       {action: 'fetch_data', cate: get_filter('cate')}
    )
    .done(function(data) {
        $('.filter_data').html(data);
    });
}