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_wp_post_revision_fields() WP 2.6.0

Determines which fields of posts are to be saved in revisions.

This is an internal function for using it by WP core itself. It's not recommended to use this function in your code.

Hooks from the function

Return

Array. Array of fields that can be versioned.

Usage

_wp_post_revision_fields( $post, $deprecated );
$post(array|WP_Post)
A post array or a WP_Post object being processed for insertion as a post revision.
Default: empty array
$deprecated(true|false)
Not used.
Default: false

Changelog

Since 2.6.0 Introduced.
Since 4.5.0 A WP_Post object can now be passed to the $post parameter.
Since 4.5.0 The optional $autosave parameter was deprecated and renamed to $deprecated.

Code of _wp_post_revision_fields() WP 5.8.2

function _wp_post_revision_fields( $post = array(), $deprecated = false ) {
	static $fields = null;

	if ( ! is_array( $post ) ) {
		$post = get_post( $post, ARRAY_A );
	}

	if ( is_null( $fields ) ) {
		// Allow these to be versioned.
		$fields = array(
			'post_title'   => __( 'Title' ),
			'post_content' => __( 'Content' ),
			'post_excerpt' => __( 'Excerpt' ),
		);
	}

	/**
	 * Filters the list of fields saved in post revisions.
	 *
	 * Included by default: 'post_title', 'post_content' and 'post_excerpt'.
	 *
	 * Disallowed fields: 'ID', 'post_name', 'post_parent', 'post_date',
	 * 'post_date_gmt', 'post_status', 'post_type', 'comment_count',
	 * and 'post_author'.
	 *
	 * @since 2.6.0
	 * @since 4.5.0 The `$post` parameter was added.
	 *
	 * @param array $fields List of fields to revision. Contains 'post_title',
	 *                      'post_content', and 'post_excerpt' by default.
	 * @param array $post   A post array being processed for insertion as a post revision.
	 */
	$fields = apply_filters( '_wp_post_revision_fields', $fields, $post );

	// WP uses these internally either in versioning or elsewhere - they cannot be versioned.
	foreach ( array( 'ID', 'post_name', 'post_parent', 'post_date', 'post_date_gmt', 'post_status', 'post_type', 'comment_count', 'post_author' ) as $protect ) {
		unset( $fields[ $protect ] );
	}

	return $fields;
}