get checked checkboxes from database - php

Question

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.
I have 3 tables:
doc_list (Stores documents)
cat_list (Stores Categories)
cat_doc_link_table (stores the doc_id & cat_id from the previous two tables)
Here are how they are formed:
CREATE TABLE `cat_doc_link_table` (
`id` int(11) NOT NULL,
`link_cat_id` int(11) NOT NULL,
`link_doc_id` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
CREATE TABLE `cat_list` (
`cat_id` int(11) NOT NULL,
`cat_title` varchar(32) NOT NULL,
`cat_color` varchar(20) NOT NULL,
`cat_icon` text NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf16 AUTO_INCREMENT=66 ;
CREATE TABLE `doc_list` (
`doc_id` int(11) NOT NULL,
`doc_title` varchar(50) NOT NULL,
`doc_content` text NOT NULL,
`doc_created` datetime NOT NULL,
`user_id` int(11) NOT NULL,
`doc_updated` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=utf16 AUTO_INCREMENT=295 ;

Answer 1

put the selected cat_id's in an array(). then use in_array() to check.
// query your db to return an array of cat_id's for the specified post.
$cats_array = array('123', '124', '156');
foreach($category as $cat){
// compare
if(in_array($cat['cat_id'], $cats_array)) {
// cat checked
}else{
// not checked
}
}