Function to check if value exists in array, check checkboxes

Question

I have a query that looks for associations between 2 tables (posts and cats), which I managed to put into an array (arrays are new to me):

$result_cats = db->query("SELECT posts_cat.cat_id
FROM posts_cat
JOIN posts ON posts_cat.post_id = posts.post_id
WHERE post_id = '$post_id'");
    
if (!$result_cats->num_rows == 0) { 
    
$rows = array();
    while ($row = $result_cats->fetch_assoc()) {
    foreach ($row as $key => $value) {
    $row[$key] = ($value);
    }
    $rows[] = $row;
    }   
}

Sample array output:

Array ( [0] => Array ( [cat_id] => 20 ) [1] => Array ( [cat_id] => 43 ) [2] => Array ( [cat_id] => 76 ) )

Now, I'd like to somehow use this in a function, to call when building checkboxes, so we can decide if they should be checked, or not.

So, for example, if 43 exists in the array, add "checked"

<input type="checkbox" id="cat_id" name="cat_id" value="43" checked>

else:

<input type="checkbox" id="cat_id" name="cat_id" value="43">

I've done something similar to this before with the following...

function checked($a,$b) 
{ 
if ($a == $b) { 
        echo " checked";
    } 
}

Then using something like:

<input type="checkbox" id="cat_id" name="cat_id" value="43" <?php echo isset($cat_id) ? checked(43,$cat_id) : "";?>>

I've been playing around with this for a while, but just can't figure out how to get it done with an array. I'm not even 100% if the way I'm thinking about this is the most efficient process. Help?

You have an array of arrays, which can be ugly to deal with sometimes. If you just have a single column (as you do), you can call fetch_all() and then use array_column to get a simpler array: stackoverflow.com/a/65893279/231316 — Chris Haas
– Chris Haas, Commented Dec 15, 2023 at 22:00
!$result_cats->num_rows == 0 doesn't do what you think it does. See Operator precedence. It should be !($result_cats->num_rows == 0) — Nick
– Nick, Commented Dec 15, 2023 at 22:15
This loop: foreach ($row as $key => $value) { $row[$key] = ($value); } doesn't do anything, it's just assigning the values you took out of the array back into it. — Nick
– Nick, Commented Dec 15, 2023 at 22:17
As @ChrisHaas suggested, you can simply dispense with the test and loop and do something like $cat_ids = array_column($result_cats->fetch_all(MYSQLI_ASSOC), 'cat_id'); then you can simply do <input type="checkbox" id="cat_id" name="cat_id" value="43" <?php echo in_array(43, $cat_ids) ? "checked" : "";?>> — Nick
– Nick, Commented Dec 15, 2023 at 22:24

TSCAmerica.com · Accepted Answer · 2023-12-15 23:48:30Z

1

Check below updated code that is streamlined to create an array of category IDs from a database query and utilize a function to efficiently determine and mark checkboxes as checked if their value matches any ID in the array.

   $result_cats = $db->query("SELECT posts_cat.cat_id FROM posts_cat JOIN posts ON posts_cat.post_id = posts.post_id WHERE post_id = '$post_id'");
    
    $cat_ids = array();
    if ($result_cats->num_rows > 0) {
        while ($row = $result_cats->fetch_assoc()) {
            $cat_ids[] = $row['cat_id'];
        }
    }
    function isChecked($cat_id, $cat_ids) {
        if (in_array($cat_id, $cat_ids)) {
            echo " checked";
        }
    }
    
    <input type="checkbox" id="cat_id" name="cat_id" value="43" <?php isChecked(43, $cat_ids); ?>>

answered Dec 15, 2023 at 23:48

TSCAmerica.com

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