diff -r 7b1b88e27a20 -r 48c4eec2b7e6 wp/wp-includes/html-api/class-wp-html-stack-event.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/html-api/class-wp-html-stack-event.php	Fri Sep 05 18:40:08 2025 +0200
@@ -0,0 +1,82 @@
+<?php
+/**
+ * HTML API: WP_HTML_Stack_Event class
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ * @since 6.6.0
+ */
+
+/**
+ * Core class used by the HTML Processor as a record for stack operations.
+ *
+ * This class is for internal usage of the WP_HTML_Processor class.
+ *
+ * @access private
+ * @since 6.6.0
+ *
+ * @see WP_HTML_Processor
+ */
+class WP_HTML_Stack_Event {
+	/**
+	 * Refers to popping an element off of the stack of open elements.
+	 *
+	 * @since 6.6.0
+	 */
+	const POP = 'pop';
+
+	/**
+	 * Refers to pushing an element onto the stack of open elements.
+	 *
+	 * @since 6.6.0
+	 */
+	const PUSH = 'push';
+
+	/**
+	 * References the token associated with the stack push event,
+	 * even if this is a pop event for that element.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @var WP_HTML_Token
+	 */
+	public $token;
+
+	/**
+	 * Indicates which kind of stack operation this event represents.
+	 *
+	 * May be one of the class constants.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @see self::POP
+	 * @see self::PUSH
+	 *
+	 * @var string
+	 */
+	public $operation;
+
+	/**
+	 * Indicates if the stack element is a real or virtual node.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @var string
+	 */
+	public $provenance;
+
+	/**
+	 * Constructor function.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param WP_HTML_Token $token      Token associated with stack event, always an opening token.
+	 * @param string        $operation  One of self::PUSH or self::POP.
+	 * @param string        $provenance "virtual" or "real".
+	 */
+	public function __construct( $token, $operation, $provenance ) {
+		$this->token      = $token;
+		$this->operation  = $operation;
+		$this->provenance = $provenance;
+	}
+}