Addon Developer Guide

{
    "id": "my-first-addon",
    "name": "My First Addon",
    "version": "1.0.0",
    "description": "A simple addon to learn the system",
    "author": "Your Name",
    "themes": ["backpage", "snet-phoenix"]
}

<?php
add_action('content_before', function() {
    echo '<div style="background:#ffe;padding:8px;text-align:center;">Hello from My First Addon!</div>';
});

{
    "id": "my-addon",
    "name": "Human-Readable Name",
    "version": "1.0.0",
    "description": "A one-line description of what this addon does.",
    "author": "Author Name",
    "author_url": "https://example.com",
    "min_app_version": "6.5.2",
    "themes": ["backpage", "snet-phoenix"],
    "admin_pages": [
        {
            "slug": "settings",
            "title": "My Addon Settings",
            "file": "admin/settings.php"
        }
    ],
    "on_install": "install.php",
    "on_update": "update.php",
    "on_uninstall": "uninstall.php"
}

add_action($hook_name, $callback, $priority);

add_action('content_before', 'run_second', 20);
add_action('content_before', 'run_first', 5);
add_action('content_before', 'run_also_second', 20);  // Same priority = order of registration

// Named function
add_action('header_nav_end', 'my_function');

// Anonymous function (closure)
add_action('footer_links', function() {
    echo '<span class="sep">&middot;</span> <a href="#">Link</a>';
});

// Object method
add_action('content_before', array($myObject, 'renderBanner'));

if (has_action('showad_after_title'))
{
    // At least one addon is hooked into showad_after_title
}

function my_showad_callback()
{
    // GOOD: Works in both themes
    global $xadid, $xsubcatid, $xad, $post;

    // AVOID: Only works in backpage (passes $post as argument)
    // function my_showad_callback($post) { ... }
}

addon_enqueue_css('my-addon', 'css/styles.css');

<link rel="stylesheet" href="https://yoursite.com/addons/my-addon/assets/css/styles.css"/>

addon_enqueue_js('my-addon', 'js/app.js');

addon_enqueue_css('my-addon', 'css/styles.css');
addon_enqueue_css('my-addon', 'css/responsive.css');
addon_enqueue_js('my-addon', 'js/vendor/library.min.js');
addon_enqueue_js('my-addon', 'js/app.js');

add_action('footer_scripts', function() {
    echo '<script>console.log("My addon loaded");</script>' . "\n";
});

add_action('head_styles', function() {
    global $xview;
    if ($xview === 'showad') {
        $url = absurl('addons/my-addon/assets/css/showad-only.css');
        echo '<link rel="stylesheet" href="' . htmlspecialchars($url) . '"/>' . "\n";
    }
});

<?php
/**
 * My Addon — Installation
 * Runs on first activation only.
 */

// Create custom table
$sql = "CREATE TABLE IF NOT EXISTS clf_myaddon_data (
    id INT AUTO_INCREMENT PRIMARY KEY,
    ad_id INT NOT NULL,
    data TEXT,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    INDEX idx_ad_id (ad_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8";
execute($sql);

<?php
/**
 * My Addon — Update
 * Runs when addon is activated with a newer version.
 * Available variables: $old_version, $new_version
 */

// v1.0.0 → v1.1.0: Add status column
if (version_compare($old_version, '1.1.0', '<'))
{
    execute("ALTER TABLE clf_myaddon_data ADD COLUMN status VARCHAR(20) DEFAULT 'active'");
}

// v1.1.0 → v1.2.0: Add index for performance
if (version_compare($old_version, '1.2.0', '<'))
{
    execute("ALTER TABLE clf_myaddon_data ADD INDEX idx_status (status)");
}

<?php
/**
 * My Addon — Uninstallation
 * Clean up all addon data.
 */

// Drop custom tables
execute("DROP TABLE IF EXISTS clf_myaddon_data");

$xz->cats        // All categories, keyed by catid
$xz->subcats     // All subcategories, keyed by subcatid
$xz->regions     // All regions/countries, keyed by countryid
$xz->cities      // All cities, keyed by cityid
$xz->areas       // All areas
$xz->params      // Request parameters
$xz->settings    // Settings instance

$cat_name = $xz->cats[$catid]['catname'];
$city_name = $xz->cities[$cityid]['cityname'];
$region_name = $xz->regions[$countryid]['countryname'];

cd addons/
zip -r my-addon.zip my-addon/

{
    "id": "email-block",
    "name": "Email Domain Blocker",
    "version": "1.0.0",
    "description": "Block ad posts from specific email domains",
    "author": "SNetworks",
    "min_app_version": "6.5.2",
    "themes": ["backpage", "snet-phoenix"],
    "admin_pages": [
        {
            "slug": "blocked-domains",
            "title": "Blocked Domains",
            "file": "admin/settings.php"
        }
    ],
    "on_install": "install.php",
    "on_uninstall": "uninstall.php"
}

<?php
$sql = "CREATE TABLE IF NOT EXISTS clf_emailblock_domains (
    id INT AUTO_INCREMENT PRIMARY KEY,
    domain VARCHAR(255) NOT NULL,
    added_on DATETIME DEFAULT CURRENT_TIMESTAMP,
    UNIQUE KEY unique_domain (domain)
) ENGINE=InnoDB DEFAULT CHARSET=utf8";
execute($sql);

<?php
execute("DROP TABLE IF EXISTS clf_emailblock_domains");

<?php
/**
 * Email Domain Blocker
 * Blocks ad submissions from blacklisted email domains.
 */

addon_enqueue_css('email-block', 'css/styles.css');

// Hook into the ad posting process
add_action('content_before', 'emailblock_check_post');

function emailblock_check_post()
{
    global $xview;

    // Only run on the post/edit views
    if ($xview !== 'post' && $xview !== 'edit') return;
    if (empty($_POST['email'])) return;

    $email = $_POST['email'];
    $domain = strtolower(substr(strrchr($email, '@'), 1));

    if (!$domain) return;

    $escaped_domain = mysql_real_escape_string($domain);
    $blocked = query_value(
        "SELECT COUNT(*) FROM clf_emailblock_domains WHERE domain = '$escaped_domain'"
    );

    if ($blocked > 0)
    {
        addon_template('email-block', 'blocked-notice', array(
            'domain' => $domain,
        ));
    }
}

<div class="bp-email-blocked-notice">
    <i class="fa fa-ban"></i>
    <strong>Posting blocked:</strong> The email domain
    <em><?php out($domain); ?></em> is not allowed.
</div>

<div class="alert alert-danger">
    <i class="fa fa-ban"></i>
    <strong>Posting blocked:</strong> The email domain
    <em><?php out($domain); ?></em> is not allowed.
</div>

<?php
// Handle adding a domain
if (($_POST['action'] ?? '') === 'add' && !empty($_POST['domain']))
{
    $domain = strtolower(trim($_POST['domain']));
    $escaped = mysql_real_escape_string($domain);
    execute("INSERT IGNORE INTO clf_emailblock_domains (domain) VALUES ('$escaped')");
    echo '<div class="msg">Domain added.</div>';
}

// Handle removing a domain
if (($_GET['action'] ?? '') === 'remove' && !empty($_GET['id']))
{
    $id = intval($_GET['id']);
    execute("DELETE FROM clf_emailblock_domains WHERE id = $id");
    echo '<div class="msg">Domain removed.</div>';
}

// Load current domains
$domains = query("SELECT * FROM clf_emailblock_domains ORDER BY domain");
$page_url = "addon-page.php?addon=email-block&page=blocked-domains";
?>

<h2>Blocked Email Domains</h2>

<form method="post" style="margin-bottom: 20px;">
    <input type="hidden" name="action" value="add" />
    <input type="text" name="domain" placeholder="example.com" size="30" />
    <button type="submit">Add Domain</button>
</form>

<?php if (!empty($domains)): ?>
<table class="datatable" width="100%">
    <tr class="head">
        <td>Domain</td>
        <td>Added On</td>
        <td width="80">Actions</td>
    </tr>
    <?php $i = 0; foreach ($domains as $d): $i++; ?>
    <tr class="<?php echo ($i % 2) ? 'row1' : 'row2'; ?>">
        <td><?php echo htmlspecialchars($d['domain']); ?></td>
        <td><?php echo htmlspecialchars($d['added_on']); ?></td>
        <td>
            <a href="<?php echo $page_url; ?>&action=remove&id=<?php echo $d['id']; ?>"
               onclick="return confirm('Remove this domain?');">Remove</a>
        </td>
    </tr>
    <?php endforeach; ?>
</table>
<?php else: ?>
<p>No domains blocked yet.</p>
<?php endif; ?>

.bp-email-blocked-notice {
    background: #ffe0e0;
    border: 1px solid #d00;
    color: #900;
    padding: 12px 16px;
    border-radius: 4px;
    margin-bottom: 16px;
}

.bp-email-blocked-notice i {
    margin-right: 6px;
}

cd addons/
zip -r email-block.zip email-block/