Traverses elements to create list from elements.

Display one element if the element doesn’t have any children otherwise, display the element and its children. Will only traverse up to the max depth and no ignore elements under that depth. It is possible to set the max depth to include all depths, see walk() method.

This method should not be called directly, use the walk() method instead.

$element object Required

Data object.

$children_elements array Required

List of elements to continue traversing (passed by reference).

$max_depth int Required

Max depth to traverse.

$depth int Required

Depth of current element.

$args array Required

An array of arguments.

$output string Required

Used to append additional content (passed by reference).

File: wp-includes/class-wp-walker.php. View all references

public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
	if ( ! $element ) {
		return;
	}

	$id_field = $this->db_fields['id'];
	$id       = $element->$id_field;

	// Display this element.
	$this->has_children = ! empty( $children_elements[ $id ] );
	if ( isset( $args[0] ) && is_array( $args[0] ) ) {
		$args[0]['has_children'] = $this->has_children; // Back-compat.
	}

	$this->start_el( $output, $element, $depth, ...array_values( $args ) );

	// Descend only when the depth is right and there are children for this element.
	if ( ( 0 == $max_depth || $max_depth > $depth + 1 ) && isset( $children_elements[ $id ] ) ) {

		foreach ( $children_elements[ $id ] as $child ) {

			if ( ! isset( $newlevel ) ) {
				$newlevel = true;
				// Start the child delimiter.
				$this->start_lvl( $output, $depth, ...array_values( $args ) );
			}
			$this->display_element( $child, $children_elements, $max_depth, $depth + 1, $args, $output );
		}
		unset( $children_elements[ $id ] );
	}

	if ( isset( $newlevel ) && $newlevel ) {
		// End the child delimiter.
		$this->end_lvl( $output, $depth, ...array_values( $args ) );
	}

	// End this element.
	$this->end_el( $output, $element, $depth, ...array_values( $args ) );
}