Auto cleanup values of “post” field when a post is deleted

inc/field.php

@@ -70,7 +70,7 @@ public static function html( $meta, $field ) {
 		return '';
 	}
 
-	protected static function begin_html( array $field ) : string {
+	protected static function begin_html( array $field ): string {
 		$id       = $field['attributes']['id'] ?? $field['id'];
 		$required = $field['required'] || ! empty( $field['attributes']['required'] );
 
@@ -101,16 +101,16 @@ protected static function begin_html( array $field ) : string {
 		return $label . $input_open;
 	}
 
-	protected static function end_html( array $field ) : string {
+	protected static function end_html( array $field ): string {
 		return RWMB_Clone::add_clone_button( $field ) . static::input_description( $field ) . '</div>';
 	}
 
-	protected static function label_description( array $field ) : string {
+	protected static function label_description( array $field ): string {
 		$id = $field['id'] ? ' id="' . esc_attr( $field['id'] ) . '-label-description"' : '';
 		return $field['label_description'] ? "<p{$id} class='description'>{$field['label_description']}</p>" : '';
 	}
 
-	protected static function input_description( array $field ) : string {
+	protected static function input_description( array $field ): string {
 		$id = $field['id'] ? ' id="' . esc_attr( $field['id'] ) . '-description"' : '';
 		return $field['desc'] ? "<p{$id} class='description'>{$field['desc']}</p>" : '';
 	}
@@ -369,7 +369,7 @@ public static function get_attributes( $field, $value = null ) {
 		return $attributes;
 	}
 
-	public static function render_attributes( array $attributes ) : string {
+	public static function render_attributes( array $attributes ): string {
 		$output = '';
 
 		$attributes = array_filter( $attributes, 'RWMB_Helpers_Value::is_valid_for_attribute' );

inc/fields/choice.php

@@ -5,6 +5,78 @@
  * The abstract choice field.
  */
 abstract class RWMB_Choice_Field extends RWMB_Field {
+
+	/**
+	 * Show field HTML
+	 * Filters are put inside this method, not inside methods such as "meta", "html", "begin_html", etc.
+	 * That ensures the returned value are always been applied filters.
+	 * This method is not meant to be overwritten in specific fields.
+	 *
+	 * @param array $field   Field parameters.
+	 * @param bool  $saved   Whether the meta box is saved at least once.
+	 * @param int   $post_id Post ID.
+	 */
+	public static function show( array $field, bool $saved, $post_id = 0 ) {
+		$meta = self::call( $field, 'meta', $post_id, $saved );
+		$meta = self::filter( 'field_meta', $meta, $field, $saved );
+
+		$meta = self::remove_options_deleted( (array) $meta, $field );
+		$meta = RWMB_Helpers_Array::array_filter_recursive( $meta );
+
+		$begin = static::begin_html( $field );
+		$begin = self::filter( 'begin_html', $begin, $field, $meta );
+
+		// Separate code for cloneable and non-cloneable fields to make easy to maintain.
+		if ( $field['clone'] ) {
+			$field_html = RWMB_Clone::html( $meta, $field );
+		} else {
+			// Call separated methods for displaying each type of field.
+			$field_html = self::call( $field, 'html', $meta );
+			$field_html = self::filter( 'html', $field_html, $field, $meta );
+		}
+
+		$end = static::end_html( $field );
+		$end = self::filter( 'end_html', $end, $field, $meta );
+
+		$html = self::filter( 'wrapper_html', "$begin$field_html$end", $field, $meta );
+
+		// Display label and input in DIV and allow user-defined classes to be appended.
+		$classes = "rwmb-field rwmb-{$field['type']}-wrapper " . $field['class'];
+		if ( ! empty( $field['required'] ) ) {
+			$classes .= ' required';
+		}
+
+		$outer_html = sprintf(
+			$field['before'] . '<div class="%s">%s</div>' . $field['after'],
+			esc_attr( trim( $classes ) ),
+			$html
+		);
+		$outer_html = self::filter( 'outer_html', $outer_html, $field, $meta );
+
+		echo $outer_html; // phpcs:ignore WordPress.Security.EscapeOutput
+	}
+
+	/**
+	 * remove_options_deleted
+	 * @param array $meta Meta value.
+	 * @param array $field Field parameters.
+	 * @return array
+	 */
+	private static function remove_options_deleted( array $meta, array $field ): array {
+		if ( ! isset( $field['options'] ) || empty( $meta ) ) {
+			return $meta;
+		}
+
+		$options = array_keys( $field['options'] );
+		array_walk_recursive($meta, function ( &$value ) use ( $options ) {
+			if ( ! empty( $value ) && ! in_array( $value, $options ) ) {
+				$value = null;
+			}
+		});
+
+		return array_filter( $meta );
+	}
+
 	/**
 	 * Get field HTML.
 	 *
@@ -37,7 +109,7 @@ public static function normalize( $field ) {
 		return $field;
 	}
 
-	public static function transform_options( $options ) : array {
+	public static function transform_options( $options ): array {
 		$transformed = [];
 		$options     = (array) $options;
 		foreach ( $options as $value => $label ) {

inc/helpers/array.php

@@ -6,4 +6,31 @@
 /**
  * No longer needed. Keep it here for backward compatibility.
  */
-class RWMB_Helpers_Array extends Arr {}
+class RWMB_Helpers_Array extends Arr {
+
+	/**
+	 * array_filter_recursive
+	 * @link https://gist.github.com/benjamw/1690140
+	 * @param array
+	 * @param string optional callback function name
+	 * @param bool optional flag removal of empty arrays after filtering
+	 * @return array merged array
+	 */
+	public static function array_filter_recursive( array $array, callable $callback = null, bool $remove_empty_arrays = false ): array {
+		foreach ( $array as $key => &$value ) { // mind the reference
+			if ( is_array( $value ) ) {
+				$value = call_user_func_array( [ 'self', 'array_filter_recursive' ], array( $value, $callback, $remove_empty_arrays ) );
+				if ( $remove_empty_arrays && ! (bool) $value ) {
+					unset( $array[ $key ] );
+				}
+			} elseif ( ! is_null( $callback ) && ! $callback( $value ) ) {
+				unset( $array[ $key ] );
+			} elseif ( ! (bool) $value ) {
+				unset( $array[ $key ] );
+			}
+		}
+		unset( $value ); // kill the reference
+
+		return array_filter( $array );
+	}
+}