WDD Custom Code Manager

Add custom CSS, JavaScript, HTML and PHP to your WordPress site — everywhere or on specific pages — without editing theme files, so nothing is lost when your theme updates.

Requirements

Installation

1. Upload the wdd-custom-code-manager folder to /wp-content/plugins/, or install the ZIP via Plugins → Add New → Upload Plugin.
2. Activate the plugin from the Plugins screen.
3. Open Code Manager in the admin menu.

On activation the plugin creates its own database table, {prefix}wdd_ccm_snippets, so snippets are independent of your theme.

Quick start

1. Go to Code Manager → Add New.
2. Enter a Title and choose the code Type.
3. Paste your code into the editor.
4. Leave Load On as Entire Site, or pick Specific Pages.
5. Make sure Status is Active, then click Save Snippet.
6. Reload your site. The change is live — no manual cache clearing needed.

Example: hide a banner on mobile

/* Type: CSS   Devices: Mobile only */
.promo-banner { display: none; }

Example: load an analytics tag in the head

<!-- Type: HTML Head   Load On: Entire Site -->
<script async src="https://example.com/tag.js"></script>

Code types

Scope

The Load On setting controls which pages receive a snippet.

Device targeting

Tick Desktop, Tablet and/or Mobile to limit a snippet to those devices. Ticking none, or all three, means no restriction.

Breakpoints

Defined in Settings → Device Breakpoints.

Breakpoints are clamped to 320–3840 px, and the tablet value is automatically held below the desktop value so the generated rules can never contradict each other.

How each type is targeted

Priority & load order

Making your code win

With Force Highest Priority on (the default), the plugin buffers the page and inserts your code after every theme and plugin hook has already run:

Nothing another plugin does on wp_head or wp_footer can land after your code, so your CSS wins the cascade against any rule of equal specificity, and your JavaScript runs last.

Ordering your own snippets

Each snippet has a numeric Priority (default 10). Lower numbers load earlier. Snippets of the same type are output in priority order; ties are broken by snippet ID, so output order is always stable.

Hook mode fallback

If another plugin conflicts with page buffering, turn Force Highest Priority off. The plugin then outputs through wp_head, wp_body_open and wp_footer at PHP_INT_MAX — still last among normal hook callbacks.

When buffering is skipped

• Admin screens, AJAX, cron, feeds, REST, XML-RPC and XML sitemaps.
• Responses that are not an HTML document.
• Requests where no active snippet needs buffering — you pay nothing on those.
• Anything you exclude with the wdd_ccm_should_buffer filter.

Cache purging

Changes are meant to appear on the very next page load. Two things make that happen.

1. The plugin's own snippet cache

Active snippets are stored in a versioned object cache so the frontend avoids a database query on every request. Every write bumps the version number, so a stale entry can never be served. Where there is no persistent object cache, a transient is used instead.

2. Third-party page caches

The following are purged automatically whenever a snippet is saved, toggled, deleted, bulk-actioned or imported, and whenever settings change:

Manual purge

• Admin bar → Purge Code Cache — available on every page while you are logged in.
• Settings → Performance & Priority → Purge Now — also lists the layers detected on your site.

Administrator bypass

While logged in as an administrator, frontend pages are sent with no-cache headers and DONOTCACHEPAGE defined, so your own reloads always show the latest code.

Settings

Found under Code Manager → Settings.

Export / Import

Export

Under Code Manager → Export / Import, click Download Export File. You get one JSON file, wdd-ccm-export-YYYY-MM-DD-HHMMSS.json, containing every snippet and the plugin settings.

{
  "plugin":   "WDD Custom Code Manager",
  "version":  "1.1.0",
  "exported": "2026-10-10 14:30:00",
  "settings": { "force_priority": 1, "desktop_breakpoint": 1025, … },
  "snippets": [
    { "title": "Hide promo on mobile", "code_type": "css", "scope": "global",
      "device_visibility": "mobile", "status": 1, "priority": 10, "code": "…" }
  ]
}

Import

Choose or drop a previously exported file, pick a mode, and click Import Now.

Tick Also import plugin settings from file to apply the file's settings as well. Caches are purged once, at the end of the import.

PHP snippets

• Disabled by default. Turn on Enable PHP Snippets in Settings.
• When disabled, PHP snippets cannot be saved and any existing ones do not run.
• Snippets execute during wp_footer, after the page content. Anything they echo is printed at that point.
• A fatal error in one snippet is caught and does not stop the page or the other snippets.
• Errors are shown as an HTML comment to administrators, and written to error_log() when WP_DEBUG is on.

// A PHP snippet — wrapping <?php ?> tags are optional
add_filter( 'the_content', function ( $content ) {
    return is_single() ? $content . '<p>Thanks for reading!</p>' : $content;
} );

Hooks & filters

Filters

Actions

Examples

// Skip a snippet on the checkout page
add_filter( 'wdd_ccm_render_snippet', function ( $render, $snippet ) {
    if ( function_exists( 'is_checkout' ) && is_checkout() ) {
        return false;
    }
    return $render;
}, 10, 2 );

// Purge a custom CDN whenever snippets change
add_action( 'wdd_ccm_purge_page_caches', function () {
    my_cdn_purge_everything();
} );

// Don't buffer pages on a path where it causes trouble
add_filter( 'wdd_ccm_should_buffer', function ( $buffer ) {
    return false !== strpos( $_SERVER['REQUEST_URI'], '/legacy-app/' ) ? false : $buffer;
} );

Troubleshooting

My changes don't show up

1. Check the snippet's Status is Active.
2. In Settings, confirm Auto-purge caches on save is on and your cache plugin is listed under Detected caching layers.
3. Click Purge Code Cache in the admin bar.
4. If you use a CDN or host-level cache that isn't listed, purge it once manually, then attach it to wdd_ccm_purge_page_caches.
5. Test in a private window — your browser may be caching the page or its assets.

My CSS is being overridden

Make sure Force Highest Priority is on. If it is, the other rule has higher specificity — see Priority & load order.

My JavaScript runs before an element exists

JavaScript is output just before </body>, so most of the page exists already. For elements added later, wait for the right moment:

document.addEventListener('DOMContentLoaded', function () {
    // safe to query the DOM here
});

A script tag or code block is cut off

A literal </script inside a JavaScript snippet is escaped automatically to stop it closing the block early. If you need a script tag, add it as an HTML Footer snippet instead.

Two copies of my code are on the page

Each code type is printed once per request. If you see duplicates, check that the same code isn't also in your theme, or saved as two snippets.

Something conflicts with page buffering

Turn Force Highest Priority off. You keep automatic cache purging and the administrator bypass.

A JavaScript snippet isn't running

Open the browser console and look for WDD CCM snippet #… — a snippet that throws is reported there with its ID.

Uninstalling

File structure

wdd-custom-code-manager/
├── wdd-custom-code-manager.php      Plugin header, constants, bootstrap, update routine
├── uninstall.php                    Cleanup on plugin deletion
├── readme.txt                       WordPress.org readme and changelog
├── CHANGELOG.md                     Developer changelog
├── docs/
│   └── index.html                   This documentation
├── includes/
│   ├── class-wdd-ccm-db.php         Table creation and schema versioning
│   ├── class-wdd-ccm-snippets.php   Snippet CRUD, bulk actions, cache invalidation
│   ├── class-wdd-ccm-settings.php   Settings storage and sanitising
│   ├── class-wdd-ccm-cache.php      Snippet cache and page-cache purging
│   ├── class-wdd-ccm-frontend.php   Frontend output and load-order handling
│   ├── class-wdd-ccm-export-import.php   JSON export and import
│   └── class-wdd-ccm-admin.php      Menus, assets, form and AJAX handlers
└── admin/
    ├── css/admin.css
    ├── js/admin.js
    └── views/                       snippets-list, snippet-editor, settings, export-import

Database table

Changelog

Follows Keep a Changelog and Semantic Versioning.