Question

Say I’ve got a mySQL database table with 4 fields:

• link_id (primary key)
• page_id
• anchor_text
• url

My data looks like this:

link_id | page_id | anchor_text | url 
1       | 1       | Link One    | http://www.one.com
2       | 1       | Link Two    | http://www.two.com
3       | 2       | Link Three  | http://www.three.com

How would I best write a function to get the links for a given page and then use that function to display them?

Function:

    function get_page_links($page_id) {

        $db = new mysqli("localhost", "root", "root", "my_db");

        //what's next?

        }

Usage:

$my_links = get_page_links(1);

//do something to parse $my_links

Display:

<a href="http://www.one.com">Link One</a>
<a href="http://www.two.com">Link Two</a>

Answer 1

$q = "SELECT *";
$q.= " FROM yourtablename";
$q.= " WHERE `page-id` = ".(int)$page_id;
$q.= " ORDER BY `link-id`";

The backticks might not be necessary, but I’m throwing them in there since you have hyphens in your field names.

Note that there is very basic validation going on here. By casting $page_id to an int before appending it, you ensure it won’t be some sort of injection attack. This isn’t a great way to do it, but it will work.

Something like mysqli_real_escape_string() is an alternative that should be considered, especially for more general sanitization.

Alternatively:

$q = sprintf("SELECT *
              FROM yourtablename
              WHERE `page-id` = %d
              ORDER BY `link-id", $page_id);

Which I like better.

---

Edit re: now what?

First off, lets not use mysqli, lets use PDO.

Second, we don’t want to connect to the database on each call of the function, we want to do this once. So move this out of the function.

// Typically this line is in another file and included once, but for now lets just
//  get this out of the function
$db = new PDO('mysql:host=localhost;dbname=my_db', 'root', 'root');

// Your function
function get_page_links($page_id) {
    // Build query
    $q = sprintf("SELECT *
                  FROM yourtablename
                  WHERE `page-id` = %d
                  ORDER BY `link-id`", $page_id);
    // Run Query
    foreach ($db->query($q) as $a) {
        printf('<a href="%s">%s</a>'."\n", $a['url'], $a['anchor-text']);
    }
}