get checked checkboxes from database

I am looknig to seek a way to get the tick boxes checked if they are assigned to the category in the database.

<?php 


try{
    // Selecting entire row from cat_list table
    $results = $dbh->query("SELECT cat_id, cat_title FROM cat_list");

}catch(Exception $e) {
    echo $e->getMessage();
    die();
}
    $category = $results->fetchAll(PDO::FETCH_ASSOC);
?>

<br>
<label><input type="checkbox" name="" class="selectall"/> Select all</label>
<div id="checkboxlist" >
<?php
    foreach($category as $cat){ 
?>

<input type="checkbox" value="<?php echo $cat["cat_id"];  ?>" <?php echo ($cat['cat_id'] == 1) ? 'checked="checked"' : ''; ?> name="cat_no[]" id="box1"> <?php echo $cat["cat_title"]; ?></a><br>

<?php
}

So when I create the post I select from the available categories which are displayed as an array, the code above is taken from my edit post form so I want it retrieve the categories I assigned to it and tick the boxes.