WP_HTML_Open_Elements

30class WP_HTML_Open_Elements {31	/**32	 * Holds the stack of open element references.33	 *34	 * @since 6.4.035	 *36	 * @var WP_HTML_Token[]37	 */38	public $stack = array();39 40	/**41	 * Whether a P element is in button scope currently.42	 *43	 * This class optimizes scope lookup by pre-calculating44	 * this value when elements are added and removed to the45	 * stack of open elements which might change its value.46	 * This avoids frequent iteration over the stack.47	 *48	 * @since 6.4.049	 *50	 * @var bool51	 */52	private $has_p_in_button_scope = false;53 54	/**55	 * A function that will be called when an item is popped off the stack of open elements.56	 *57	 * The function will be called with the popped item as its argument.58	 *59	 * @since 6.6.060	 *61	 * @var Closure|null62	 */63	private $pop_handler = null;64 65	/**66	 * A function that will be called when an item is pushed onto the stack of open elements.67	 *68	 * The function will be called with the pushed item as its argument.69	 *70	 * @since 6.6.071	 *72	 * @var Closure|null73	 */74	private $push_handler = null;75 76	/**77	 * Sets a pop handler that will be called when an item is popped off the stack of78	 * open elements.79	 *80	 * The function will be called with the pushed item as its argument.81	 *82	 * @since 6.6.083	 *84	 * @param Closure $handler The handler function.85	 */86	public function set_pop_handler( Closure $handler ): void {87		$this->pop_handler = $handler;88	}89 90	/**91	 * Sets a push handler that will be called when an item is pushed onto the stack of92	 * open elements.93	 *94	 * The function will be called with the pushed item as its argument.95	 *96	 * @since 6.6.097	 *98	 * @param Closure $handler The handler function.99	 */100	public function set_push_handler( Closure $handler ): void {101		$this->push_handler = $handler;102	}103 104	/**105	 * Returns the name of the node at the nth position on the stack106	 * of open elements, or `null` if no such position exists.107	 *108	 * Note that this uses a 1-based index, which represents the109	 * "nth item" on the stack, counting from the top, where the