wp-email-templates

name

wp-email-templates

description

Use when adding or refactoring transactional emails in a WordPress plugin — extracting inline HTML strings into reusable templates sharing a branded base shell, implementing the render_template helper (ob_start / include / ob_get_clean), passing variables safely with extract(EXTR_SKIP), sending via wp_mail(), testing with MockPHPMailer / tests_retrieve_phpmailer_instance(), applying table-based HTML layout and inline CSS for email clients, or handling wp_mail send-failure branches. Triggers: "send an email from my plugin", "wp_mail not working", "add an email template", "style my plugin emails", "HTML email in WordPress", "branded email wrapper", "email not arriving", "test my wp_mail", "add a CTA button to the email", "make emails look good in Outlook", "transactional email template", "render_template helper", "ob_start for email", "extract EXTR_SKIP", "MockPHPMailer in tests", "tests_retrieve_phpmailer_instance", "pre_wp_mail filter to test failure", "inline CSS email", "dark mode email support", "table-based email layout", "wp_mail headers", "email not sending in tests". Not for: REST API webhooks, push notifications, or transactional email in themes.

Reusable HTML Email Templates (WordPress plugin)

Model note: Mechanical refactoring — extract strings, create template files, wire wp_mail(). haiku handles end-to-end.

Move email bodies out of inline PHP strings into templates/emails/, where every message reuses one branded shell. Adding a new email = adding one content file.

When to use

• "Move email content to templates", "branded/HTML emails", "reuse an email template".
• Any plugin building messages inline with wp_mail() heredocs.

Not for: REST API webhooks, push notifications, or Slack integrations. Transactional email in themes — this skill targets plugin-delivered mail only.

Structure

templates/emails/
  base.php          shared shell: header, body slot ($content), footer
  <name>.php        per-email content (greeting, copy, CTA button)

• base.php — table-based, inline-CSS responsive shell (email clients ignore <style>/external CSS). Receives $subject, $preheader, $content, $site_name, $site_url. Echoes $content raw (// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped — content templates escape their own values).
• content templates — escape every variable (esc_html, esc_url); wrap copy in __()/esc_html__() with the text domain; use _n() for plurals. Guard each $var = $var ?? default; so the file is robust if rendered standalone.

Render helpers (in your Helpers class)

public static function render_template( string $path, array $vars = [] ): string {
    if ( ! is_readable( $path ) ) return '';
    // phpcs:ignore WordPress.PHP.DontExtract.extract_extract -- controlled template vars
    extract( $vars, EXTR_SKIP );
    ob_start();
    include $path;
    return (string) ob_get_clean();
}

public static function render_email( string $template, array $vars = [] ): string {
    $dir = (string) plugin_config( 'templates' ) . 'emails/';   // your assets/templates path helper
    $vars['content']   = self::render_template( $dir . $template . '.php', $vars );
    $vars['site_name'] = $vars['site_name'] ?? get_bloginfo( 'name' );
    $vars['site_url']  = $vars['site_url'] ?? home_url( '/' );
    return self::render_template( $dir . 'base.php', $vars );   // always wrap in the shell
}

A missing content template yields an empty body but the shell still renders — callers always get a valid document.

Sending

$body    = Helpers::render_email( 'welcome', [ 'subject' => $subject, 'user_name' => $u->display_name, ... ] );
$headers = [ 'Content-Type: text/html; charset=UTF-8' ];   // REQUIRED for HTML
return wp_mail( $to, $subject, $body, $headers );

Drive any TTL/expiry copy from the same constant the code uses (e.g. a token transient TTL) so email text can't drift from behavior.

Gotchas

• Entities in translated strings: © double-escapes through esc_html__ → use the literal ©.
• Don't assign WordPress globals in templates ($year etc. trip WordPress.WP.GlobalVariablesOverride) — inline gmdate('Y') instead.

Testing

WP's test suite captures wp_mail via MockPHPMailer:

reset_phpmailer_instance();
// ... trigger the send ...
$sent = tests_retrieve_phpmailer_instance()->get_sent();
$this->assertStringContainsString( 'text/html', $sent->header );
$this->assertStringContainsString( '<!DOCTYPE html', $sent->body );   // base shell used
$this->assertStringContainsString( $expected_cta, $sent->body );

Force a send failure with add_filter( 'pre_wp_mail', '__return_false' ) to test the error branch.

References

• references/base.php — the full responsive HTML base shell (header/body/footer, inline CSS), copy into templates/emails/base.php.
• references/content-example.php — an example content template (greeting, CTA button, optional expiry, fallback link) to copy and adapt per email.
• references/html-email-patterns.md — HTML email patterns: table-based layout rules, inline CSS requirements, dark-mode support, and Outlook-specific fixes
• references/wp-mail-api.md — WordPress mail API reference: wp_mail() parameters, phpmailer_init hook, SMTP configuration, and deliverability checklist