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WPSEO_Meta{} Yoast 1.0

This class implements defaults and value validation for all WPSEO Post Meta values.

Some guidelines:

  • To update a meta value, you can just use update_post_meta() with the full (prefixed) meta key or the convenience method WPSEO_Meta::set_value() with the internal key. All updates will be automatically validated. Meta values will only be saved to the database if they are not the same as the default to keep database load low.
  • To retrieve a WPSEO meta value, you must use WPSEO_Meta::get_value() which will always return a string value, either the saved value or the default. This method can also retrieve a complete set of WPSEO meta values for one specific post, see the method documentation for the parameters.

{@internal Unfortunately there isn't a filter available to hook into before returning the results for get_post_meta(), get_post_custom() and the likes. That would have been the preferred solution.}}

{@internal All WP native get_meta() results get cached internally, so no need to cache locally.}} {@internal Use $key when the key is the WPSEO internal name (without prefix), $meta_key when it includes the prefix.}}

Возвращает

null. Ничего.

Использование

$WPSEO_Meta = new WPSEO_Meta();
// use class methods

Методы

  1. array_merge_recursive_distinct()
  2. clean_up()
  3. delete( $key, $post_id )
  4. dont_save_meta_if_default( $check, $object_id, $meta_key, $meta_value )
  5. get_meta_field_defs( $tab, $post_type = 'post' )
  6. get_value( $key, $postid = 0 )
  7. init()
  8. keyword_usage( $keyword, $post_id )
  9. meta_value_is_default( $meta_key, $meta_value )
  10. remove_meta_if_default( $check, $object_id, $meta_key, $meta_value, $prev_value = '' )
  11. replace_meta( $old_metakey, $new_metakey, $delete_old = false )
  12. sanitize_post_meta( $meta_value, $meta_key )
  13. set_value( $key, $meta_value, $post_id )
  14. validate_meta_robots_adv( $meta_value )

Код WPSEO_Meta{} Yoast 17.3

class WPSEO_Meta {

	/**
	 * Prefix for all WPSEO meta values in the database.
	 *
	 * {@internal If at any point this would change, quite apart from an upgrade routine,
	 *            this also will need to be changed in the wpml-config.xml file.}}
	 *
	 * @var string
	 */
	public static $meta_prefix = '_yoast_wpseo_';

	/**
	 * Prefix for all WPSEO meta value form field names and ids.
	 *
	 * @var string
	 */
	public static $form_prefix = 'yoast_wpseo_';

	/**
	 * Allowed length of the meta description.
	 *
	 * @var int
	 */
	public static $meta_length = 156;

	/**
	 * Reason the meta description is not the default length.
	 *
	 * @var string
	 */
	public static $meta_length_reason = '';

	/**
	 * Meta box field definitions for the meta box form.
	 *
	 * {@internal
	 * - Titles, help texts, description text and option labels are added via a translate_meta_boxes() method
	 *   in the relevant child classes (WPSEO_Metabox and WPSEO_Social_admin) as they are only needed there.
	 * - Beware: even though the meta keys are divided into subsets, they still have to be uniquely named!}}
	 *
	 * @var array
	 *            Array format:
	 *                (required)       'type'          => (string) field type. i.e. text / textarea / checkbox /
	 *                                                    radio / select / multiselect / upload etc.
	 *                (required)       'title'         => (string) table row title.
	 *                (recommended)    'default_value' => (string|array) default value for the field.
	 *                                                    IMPORTANT:
	 *                                                    - if the field has options, the default has to be the
	 *                                                      key of one of the options.
	 *                                                    - if the field is a text field, the default **has** to be
	 *                                                      an empty string as otherwise the user can't save
	 *                                                      an empty value/delete the meta value.
	 *                                                    - if the field is a checkbox, the only valid values
	 *                                                      are 'on' or 'off'.
	 *                (semi-required)   'options'      => (array) options for used with (multi-)select and radio
	 *                                                    fields, required if that's the field type.
	 *                                                    key = (string) value which will be saved to db.
	 *                                                    value = (string) text label for the option.
	 *                (optional)        'autocomplete' => (bool) whether autocomplete is on for text fields,
	 *                                                    defaults to true.
	 *                (optional)        'class'        => (string) classname(s) to add to the actual <input> tag.
	 *                (optional)        'description'  => (string) description to show underneath the field.
	 *                (optional)        'expl'         => (string) label for a checkbox.
	 *                (optional)        'help'         => (string) help text to show on mouse over ? image.
	 *                (optional)        'rows'         => (int) number of rows for a textarea, defaults to 3.
	 *                (optional)        'placeholder'  => (string) Currently only used by add-on plugins.
	 *                (optional)        'serialized'   => (bool) whether the value is expected to be serialized,
	 *                                                     i.e. an array or object, defaults to false.
	 *                                                     Currently only used by add-on plugins.
	 */
	public static $meta_fields = [
		'general'  => [
			'focuskw'        => [
				'type'  => 'hidden',
				'title' => '',
			],
			'title'          => [
				'type'          => 'hidden',
				'title'         => '', // Translation added later.
				'default_value' => '',
				'description'   => '', // Translation added later.
				'help'          => '', // Translation added later.
			],
			'metadesc'       => [
				'type'          => 'hidden',
				'title'         => '', // Translation added later.
				'default_value' => '',
				'class'         => 'metadesc',
				'rows'          => 2,
				'description'   => '', // Translation added later.
				'help'          => '', // Translation added later.
			],
			'linkdex'        => [
				'type'          => 'hidden',
				'title'         => 'linkdex',
				'default_value' => '0',
				'description'   => '',
			],
			'content_score'  => [
				'type'          => 'hidden',
				'title'         => 'content_score',
				'default_value' => '0',
				'description'   => '',
			],
			'is_cornerstone' => [
				'type'          => 'hidden',
				'title'         => 'is_cornerstone',
				'default_value' => 'false',
				'description'   => '',
			],
		],
		'advanced' => [
			'meta-robots-noindex'  => [
				'type'          => 'hidden',
				'title'         => '', // Translation added later.
				'default_value' => '0', // = post-type default.
				'options'       => [
					'0' => '', // Post type default - translation added later.
					'2' => '', // Index - translation added later.
					'1' => '', // No-index - translation added later.
				],
			],
			'meta-robots-nofollow' => [
				'type'          => 'hidden',
				'title'         => '', // Translation added later.
				'default_value' => '0', // = follow.
				'options'       => [
					'0' => '', // Follow - translation added later.
					'1' => '', // No-follow - translation added later.
				],
			],
			'meta-robots-adv'      => [
				'type'          => 'hidden',
				'title'         => '', // Translation added later.
				'default_value' => '',
				'description'   => '', // Translation added later.
				'options'       => [
					'noimageindex' => '', // Translation added later.
					'noarchive'    => '', // Translation added later.
					'nosnippet'    => '', // Translation added later.
				],
			],
			'bctitle'              => [
				'type'          => 'hidden',
				'title'         => '', // Translation added later.
				'default_value' => '',
				'description'   => '', // Translation added later.
			],
			'canonical'            => [
				'type'          => 'hidden',
				'title'         => '', // Translation added later.
				'default_value' => '',
				'description'   => '', // Translation added later.
			],
			'redirect'             => [
				'type'          => 'url',
				'title'         => '', // Translation added later.
				'default_value' => '',
				'description'   => '', // Translation added later.
			],
		],
		'social'   => [],
		'schema'   => [
			'schema_page_type'    => [
				'type'    => 'hidden',
				'title'   => '',
				'options' => Schema_Types::PAGE_TYPES,
			],
			'schema_article_type' => [
				'type'          => 'hidden',
				'title'         => '',
				'hide_on_pages' => true,
				'options'       => Schema_Types::ARTICLE_TYPES,
			],
		],
		/* Fields we should validate & save, but not show on any form. */
		'non_form' => [
			'linkdex' => [
				'type'          => null,
				'default_value' => '0',
			],
			'zapier_trigger_sent' => [
				'type'          => null,
				'default_value' => '0',
			],
		],
	];

	/**
	 * Helper property - reverse index of the definition array.
	 *
	 * Format: [full meta key including prefix]    => array
	 *         ['subset']    => (string) primary index
	 *         ['key']       => (string) internal key
	 *
	 * @var array
	 */
	public static $fields_index = [];

	/**
	 * Helper property - array containing only the defaults in the format:
	 * [full meta key including prefix]    => (string) default value
	 *
	 * @var array
	 */
	public static $defaults = [];

	/**
	 * Helper property to define the social network meta field definitions - networks.
	 *
	 * @var array
	 */
	private static $social_networks = [
		'opengraph'  => 'opengraph',
		'twitter'    => 'twitter',
	];

	/**
	 * Helper property to define the social network meta field definitions - fields and their type.
	 *
	 * @var array
	 */
	private static $social_fields = [
		'title'       => 'hidden',
		'description' => 'hidden',
		'image'       => 'hidden',
		'image-id'    => 'hidden',
	];

	/**
	 * Register our actions and filters.
	 *
	 * @return void
	 */
	public static function init() {
		foreach ( self::$social_networks as $option => $network ) {
			if ( WPSEO_Options::get( $option, false ) === true ) {
				foreach ( self::$social_fields as $box => $type ) {
					self::$meta_fields['social'][ $network . '-' . $box ] = [
						'type'          => $type,
						'title'         => '', // Translation added later.
						'default_value' => '',
						'description'   => '', // Translation added later.
					];
				}
			}
		}
		unset( $option, $network, $box, $type );

		/**
		 * Allow add-on plugins to register their meta fields for management by this class.
		 * Calls to add_filter() must be made before plugins_loaded prio 14.
		 */
		$extra_fields = apply_filters( 'add_extra_wpseo_meta_fields', [] );
		if ( is_array( $extra_fields ) ) {
			self::$meta_fields = self::array_merge_recursive_distinct( $extra_fields, self::$meta_fields );
		}
		unset( $extra_fields );

		foreach ( self::$meta_fields as $subset => $field_group ) {
			foreach ( $field_group as $key => $field_def ) {

				register_meta(
					'post',
					self::$meta_prefix . $key,
					[ 'sanitize_callback' => [ __CLASS__, 'sanitize_post_meta' ] ]
				);

				// Set the $fields_index property for efficiency.
				self::$fields_index[ self::$meta_prefix . $key ] = [
					'subset' => $subset,
					'key'    => $key,
				];

				// Set the $defaults property for efficiency.
				if ( isset( $field_def['default_value'] ) ) {
					self::$defaults[ self::$meta_prefix . $key ] = $field_def['default_value'];
				}
				else {
					// Meta will always be a string, so let's make the meta meta default also a string.
					self::$defaults[ self::$meta_prefix . $key ] = '';
				}
			}
		}
		unset( $subset, $field_group, $key, $field_def );

		add_filter( 'update_post_metadata', [ __CLASS__, 'remove_meta_if_default' ], 10, 5 );
		add_filter( 'add_post_metadata', [ __CLASS__, 'dont_save_meta_if_default' ], 10, 4 );
	}

	/**
	 * Retrieve the meta box form field definitions for the given tab and post type.
	 *
	 * @param string $tab       Tab for which to retrieve the field definitions.
	 * @param string $post_type Post type of the current post.
	 *
	 * @return array Array containing the meta box field definitions.
	 */
	public static function get_meta_field_defs( $tab, $post_type = 'post' ) {
		if ( ! isset( self::$meta_fields[ $tab ] ) ) {
			return [];
		}

		$field_defs = self::$meta_fields[ $tab ];

		switch ( $tab ) {
			case 'non-form':
				// Prevent non-form fields from being passed to forms.
				$field_defs = [];
				break;

			case 'advanced':
				global $post;

				if ( ! WPSEO_Capability_Utils::current_user_can( 'wpseo_edit_advanced_metadata' ) && WPSEO_Options::get( 'disableadvanced_meta' ) ) {
					return [];
				}

				$post_type = '';
				if ( isset( $post->post_type ) ) {
					$post_type = $post->post_type;
				}
				elseif ( ! isset( $post->post_type ) && isset( $_GET['post_type'] ) ) {
					$post_type = sanitize_text_field( $_GET['post_type'] );
				}

				if ( $post_type === '' ) {
					return [];
				}

				/* Adjust the no-index text strings based on the post type. */
				$post_type_object = get_post_type_object( $post_type );

				$field_defs['meta-robots-noindex']['title']        = sprintf( $field_defs['meta-robots-noindex']['title'], $post_type_object->labels->singular_name );
				$field_defs['meta-robots-noindex']['options']['0'] = sprintf( $field_defs['meta-robots-noindex']['options']['0'], ( ( WPSEO_Options::get( 'noindex-' . $post_type, false ) === true ) ? $field_defs['meta-robots-noindex']['options']['1'] : $field_defs['meta-robots-noindex']['options']['2'] ), $post_type_object->label );
				$field_defs['meta-robots-nofollow']['title']       = sprintf( $field_defs['meta-robots-nofollow']['title'], $post_type_object->labels->singular_name );

				/* Don't show the breadcrumb title field if breadcrumbs aren't enabled. */
				if ( WPSEO_Options::get( 'breadcrumbs-enable', false ) !== true && ! current_theme_supports( 'yoast-seo-breadcrumbs' ) ) {
					unset( $field_defs['bctitle'] );
				}

				global $post;

				if ( empty( $post->ID ) || ( ! empty( $post->ID ) && self::get_value( 'redirect', $post->ID ) === '' ) ) {
					unset( $field_defs['redirect'] );
				}
				break;

			case 'schema':
				if ( ! WPSEO_Capability_Utils::current_user_can( 'wpseo_edit_advanced_metadata' ) && WPSEO_Options::get( 'disableadvanced_meta' ) ) {
					return [];
				}

				$field_defs['schema_page_type']['default'] = WPSEO_Options::get( 'schema-page-type-' . $post_type );

				$article_helper = new Article_Helper();
				if ( $post_type !== 'page' && $article_helper->is_author_supported( $post_type ) ) {
					$field_defs['schema_article_type']['default'] = WPSEO_Options::get( 'schema-article-type-' . $post_type );
				}
				else {
					unset( $field_defs['schema_article_type'] );
				}

				break;
		}

		/**
		 * Filter the WPSEO metabox form field definitions for a tab.
		 * {tab} can be 'general', 'advanced' or 'social'.
		 *
		 * @param array  $field_defs Metabox form field definitions.
		 * @param string $post_type  Post type of the post the metabox is for, defaults to 'post'.
		 *
		 * @return array
		 */
		return apply_filters( 'wpseo_metabox_entries_' . $tab, $field_defs, $post_type );
	}

	/**
	 * Validate the post meta values.
	 *
	 * @param mixed  $meta_value The new value.
	 * @param string $meta_key   The full meta key (including prefix).
	 *
	 * @return string Validated meta value.
	 */
	public static function sanitize_post_meta( $meta_value, $meta_key ) {
		$field_def = self::$meta_fields[ self::$fields_index[ $meta_key ]['subset'] ][ self::$fields_index[ $meta_key ]['key'] ];
		$clean     = self::$defaults[ $meta_key ];

		switch ( true ) {
			case ( $meta_key === self::$meta_prefix . 'linkdex' ):
				$int = WPSEO_Utils::validate_int( $meta_value );
				if ( $int !== false && $int >= 0 ) {
					$clean = strval( $int ); // Convert to string to make sure default check works.
				}
				break;

			case ( $field_def['type'] === 'checkbox' ):
				// Only allow value if it's one of the predefined options.
				if ( in_array( $meta_value, [ 'on', 'off' ], true ) ) {
					$clean = $meta_value;
				}
				break;


			case ( $field_def['type'] === 'select' || $field_def['type'] === 'radio' ):
				// Only allow value if it's one of the predefined options.
				if ( isset( $field_def['options'][ $meta_value ] ) ) {
					$clean = $meta_value;
				}
				break;


			case ( $field_def['type'] === 'hidden' && $meta_key === self::$meta_prefix . 'meta-robots-adv' ):
				$clean = self::validate_meta_robots_adv( $meta_value );
				break;


			case ( $field_def['type'] === 'url' || $meta_key === self::$meta_prefix . 'canonical' ):
				// Validate as url(-part).
				$url = WPSEO_Utils::sanitize_url( $meta_value );
				if ( $url !== '' ) {
					$clean = $url;
				}
				break;


			case ( $field_def['type'] === 'upload' && in_array( $meta_key, [ self::$meta_prefix . 'opengraph-image', self::$meta_prefix . 'twitter-image' ], true ) ):
				// Validate as url.
				$url = WPSEO_Utils::sanitize_url( $meta_value, [ 'http', 'https', 'ftp', 'ftps' ] );
				if ( $url !== '' ) {
					$clean = $url;
				}
				break;

			case ( $field_def['type'] === 'hidden' && $meta_key === self::$meta_prefix . 'is_cornerstone' ):
				$clean = $meta_value;

				/*
				 * This used to be a checkbox, then became a hidden input.
				 * To make sure the value remains consistent, we cast 'true' to '1'.
				 */
				if ( $meta_value === 'true' ) {
					$clean = '1';
				}
				break;

			case ( $field_def['type'] === 'hidden' && isset( $field_def['options'] ) ):
				// Only allow value if it's one of the predefined options.
				if ( isset( $field_def['options'][ $meta_value ] ) ) {
					$clean = $meta_value;
				}
				break;

			case ( $field_def['type'] === 'textarea' ):
				if ( is_string( $meta_value ) ) {
					// Remove line breaks and tabs.
					// @todo [JRF => Yoast] Verify that line breaks and the likes aren't allowed/recommended in meta header fields.
					$meta_value = str_replace( [ "\n", "\r", "\t", '  ' ], ' ', $meta_value );
					$clean      = WPSEO_Utils::sanitize_text_field( trim( $meta_value ) );
				}
				break;

			case ( $field_def['type'] === 'multiselect' ):
				$clean = $meta_value;
				break;


			case ( $field_def['type'] === 'text' ):
			default:
				if ( is_string( $meta_value ) ) {
					$clean = WPSEO_Utils::sanitize_text_field( trim( $meta_value ) );
				}

				break;
		}

		$clean = apply_filters( 'wpseo_sanitize_post_meta_' . $meta_key, $clean, $meta_value, $field_def, $meta_key );

		return $clean;
	}

	/**
	 * Validate a meta-robots-adv meta value.
	 *
	 * @todo [JRF => Yoast] Verify that this logic for the prioritisation is correct.
	 *
	 * @param array|string $meta_value The value to validate.
	 *
	 * @return string Clean value.
	 */
	public static function validate_meta_robots_adv( $meta_value ) {
		$clean   = self::$meta_fields['advanced']['meta-robots-adv']['default_value'];
		$options = self::$meta_fields['advanced']['meta-robots-adv']['options'];

		if ( is_string( $meta_value ) ) {
			$meta_value = explode( ',', $meta_value );
		}

		if ( is_array( $meta_value ) && $meta_value !== [] ) {
			$meta_value = array_map( 'trim', $meta_value );

			// Individual selected entries.
			$cleaning = [];
			foreach ( $meta_value as $value ) {
				if ( isset( $options[ $value ] ) ) {
					$cleaning[] = $value;
				}
			}

			if ( $cleaning !== [] ) {
				$clean = implode( ',', $cleaning );
			}
			unset( $cleaning, $value );
		}

		return $clean;
	}

	/**
	 * Prevent saving of default values and remove potential old value from the database if replaced by a default.
	 *
	 * @param bool   $check      The current status to allow updating metadata for the given type.
	 * @param int    $object_id  ID of the current object for which the meta is being updated.
	 * @param string $meta_key   The full meta key (including prefix).
	 * @param string $meta_value New meta value.
	 * @param string $prev_value The old meta value.
	 *
	 * @return bool|null True = stop saving, null = continue saving.
	 */
	public static function remove_meta_if_default( $check, $object_id, $meta_key, $meta_value, $prev_value = '' ) {
		/* If it's one of our meta fields, check against default. */
		if ( isset( self::$fields_index[ $meta_key ] ) && self::meta_value_is_default( $meta_key, $meta_value ) === true ) {
			if ( $prev_value !== '' ) {
				delete_post_meta( $object_id, $meta_key, $prev_value );
			}
			else {
				delete_post_meta( $object_id, $meta_key );
			}

			return true; // Stop saving the value.
		}

		return $check; // Go on with the normal execution (update) in meta.php.
	}

	/**
	 * Prevent adding of default values to the database.
	 *
	 * @param bool   $check      The current status to allow adding metadata for the given type.
	 * @param int    $object_id  ID of the current object for which the meta is being added.
	 * @param string $meta_key   The full meta key (including prefix).
	 * @param string $meta_value New meta value.
	 *
	 * @return bool|null True = stop saving, null = continue saving.
	 */
	public static function dont_save_meta_if_default( $check, $object_id, $meta_key, $meta_value ) {
		/* If it's one of our meta fields, check against default. */
		if ( isset( self::$fields_index[ $meta_key ] ) && self::meta_value_is_default( $meta_key, $meta_value ) === true ) {
			return true; // Stop saving the value.
		}

		return $check; // Go on with the normal execution (add) in meta.php.
	}

	/**
	 * Is the given meta value the same as the default value ?
	 *
	 * @param string $meta_key   The full meta key (including prefix).
	 * @param mixed  $meta_value The value to check.
	 *
	 * @return bool
	 */
	public static function meta_value_is_default( $meta_key, $meta_value ) {
		return ( isset( self::$defaults[ $meta_key ] ) && $meta_value === self::$defaults[ $meta_key ] );
	}

	/**
	 * Get a custom post meta value.
	 *
	 * Returns the default value if the meta value has not been set.
	 *
	 * {@internal Unfortunately there isn't a filter available to hook into before returning
	 *            the results for get_post_meta(), get_post_custom() and the likes. That
	 *            would have been the preferred solution.}}
	 *
	 * @param string $key    Internal key of the value to get (without prefix).
	 * @param int    $postid Post ID of the post to get the value for.
	 *
	 * @return string All 'normal' values returned from get_post_meta() are strings.
	 *                Objects and arrays are possible, but not used by this plugin
	 *                and therefore discarted (except when the special 'serialized' field def
	 *                value is set to true - only used by add-on plugins for now).
	 *                Will return the default value if no value was found.
	 *                Will return empty string if no default was found (not one of our keys) or
	 *                if the post does not exist.
	 */
	public static function get_value( $key, $postid = 0 ) {
		global $post;

		$postid = absint( $postid );
		if ( $postid === 0 ) {
			if ( ( isset( $post ) && is_object( $post ) ) && ( isset( $post->post_status ) && $post->post_status !== 'auto-draft' ) ) {
				$postid = $post->ID;
			}
			else {
				return '';
			}
		}

		$custom    = get_post_custom( $postid ); // Array of strings or empty array.
		$table_key = self::$meta_prefix . $key;

		// Populate the field_def using the field_index lookup array.
		$field_def = [];
		if ( isset( self::$fields_index[ $table_key ] ) ) {
			$field_def = self::$meta_fields[ self::$fields_index[ $table_key ]['subset'] ][ self::$fields_index[ $table_key ]['key'] ];
		}

		// Check if we have a custom post meta entry.
		if ( isset( $custom[ $table_key ][0] ) ) {
			$unserialized = maybe_unserialize( $custom[ $table_key ][0] );

			// Check if it is already unserialized.
			if ( $custom[ $table_key ][0] === $unserialized ) {
				return $custom[ $table_key ][0];
			}

			// Check whether we need to unserialize it.
			if ( isset( $field_def['serialized'] ) && $field_def['serialized'] === true ) {
				// Ok, serialize value expected/allowed.
				return $unserialized;
			}
		}

		// Meta was either not found or found, but object/array while not allowed to be.
		if ( isset( self::$defaults[ self::$meta_prefix . $key ] ) ) {
			// Update the default value to the current post type.
			switch ( $key ) {
				case 'schema_page_type':
				case 'schema_article_type':
					return '';
			}

			return self::$defaults[ self::$meta_prefix . $key ];
		}

		/*
		 * Shouldn't ever happen, means not one of our keys as there will always be a default available
		 * for all our keys.
		 */
		return '';
	}

	/**
	 * Update a meta value for a post.
	 *
	 * @param string $key        The internal key of the meta value to change (without prefix).
	 * @param mixed  $meta_value The value to set the meta to.
	 * @param int    $post_id    The ID of the post to change the meta for.
	 *
	 * @return bool Whether the value was changed.
	 */
	public static function set_value( $key, $meta_value, $post_id ) {
		/*
		 * Slash the data, because `update_metadata` will unslash it and we have already unslashed it.
		 * Related issue: https://github.com/Yoast/YoastSEO.js/issues/2158
		 */
		$meta_value = wp_slash( $meta_value );

		return update_post_meta( $post_id, self::$meta_prefix . $key, $meta_value );
	}

	/**
	 * Deletes a meta value for a post.
	 *
	 * @param string $key     The internal key of the meta value to change (without prefix).
	 * @param int    $post_id The ID of the post to change the meta for.
	 *
	 * @return bool Whether the value was changed.
	 */
	public static function delete( $key, $post_id ) {
		return delete_post_meta( $post_id, self::$meta_prefix . $key );
	}

	/**
	 * Used for imports, this functions imports the value of $old_metakey into $new_metakey for those post
	 * where no WPSEO meta data has been set.
	 * Optionally deletes the $old_metakey values.
	 *
	 * @param string $old_metakey The old key of the meta value.
	 * @param string $new_metakey The new key, usually the WPSEO meta key (including prefix).
	 * @param bool   $delete_old  Whether to delete the old meta key/value-sets.
	 *
	 * @return void
	 */
	public static function replace_meta( $old_metakey, $new_metakey, $delete_old = false ) {
		global $wpdb;

		/*
		 * Get only those rows where no wpseo meta values exist for the same post
		 * (with the exception of linkdex as that will be set independently of whether the post has been edited).
		 *
		 * {@internal Query is pretty well optimized this way.}}
		 */
		$query  = $wpdb->prepare(
			"
				SELECT `a`.*
				FROM {$wpdb->postmeta} AS a
				WHERE `a`.`meta_key` = %s
					AND NOT	EXISTS (
						SELECT DISTINCT `post_id` , count( `meta_id` ) AS count
						FROM {$wpdb->postmeta} AS b
						WHERE `a`.`post_id` = `b`.`post_id`
							AND `meta_key` LIKE %s
							AND `meta_key` <> %s
						GROUP BY `post_id`
					)
				;",
			$old_metakey,
			$wpdb->esc_like( self::$meta_prefix . '%' ),
			self::$meta_prefix . 'linkdex'
		);
		$oldies = $wpdb->get_results( $query );

		if ( is_array( $oldies ) && $oldies !== [] ) {
			foreach ( $oldies as $old ) {
				update_post_meta( $old->post_id, $new_metakey, $old->meta_value );
			}
		}

		// Delete old keys.
		if ( $delete_old === true ) {
			delete_post_meta_by_key( $old_metakey );
		}
	}

	/**
	 * General clean-up of the saved meta values.
	 * - Remove potentially lingering old meta keys;
	 * - Remove all default and invalid values.
	 *
	 * @return void
	 */
	public static function clean_up() {
		global $wpdb;

		/*
		 * Clean up '_yoast_wpseo_meta-robots'.
		 *
		 * Retrieve all '_yoast_wpseo_meta-robots' meta values and convert if no new values found.
		 *
		 * {@internal Query is pretty well optimized this way.}}
		 *
		 * @todo [JRF => Yoast] Find out all possible values which the old '_yoast_wpseo_meta-robots' could contain
		 * to convert the data correctly.
		 */
		$query  = $wpdb->prepare(
			"
				SELECT `a`.*
				FROM {$wpdb->postmeta} AS a
				WHERE `a`.`meta_key` = %s
					AND NOT	EXISTS (
						SELECT DISTINCT `post_id` , count( `meta_id` ) AS count
						FROM {$wpdb->postmeta} AS b
						WHERE `a`.`post_id` = `b`.`post_id`
							AND ( `meta_key` = %s
							OR `meta_key` = %s )
						GROUP BY `post_id`
					)
				;",
			self::$meta_prefix . 'meta-robots',
			self::$meta_prefix . 'meta-robots-noindex',
			self::$meta_prefix . 'meta-robots-nofollow'
		);
		$oldies = $wpdb->get_results( $query );

		if ( is_array( $oldies ) && $oldies !== [] ) {
			foreach ( $oldies as $old ) {
				$old_values = explode( ',', $old->meta_value );
				foreach ( $old_values as $value ) {
					if ( $value === 'noindex' ) {
						update_post_meta( $old->post_id, self::$meta_prefix . 'meta-robots-noindex', 1 );
					}
					elseif ( $value === 'nofollow' ) {
						update_post_meta( $old->post_id, self::$meta_prefix . 'meta-robots-nofollow', 1 );
					}
				}
			}
		}
		unset( $query, $oldies, $old, $old_values, $value );

		// Delete old keys.
		delete_post_meta_by_key( self::$meta_prefix . 'meta-robots' );

		/*
		 * Remove all default values and (most) invalid option values.
		 * Invalid option values for the multiselect (meta-robots-adv) field will be dealt with seperately.
		 *
		 * {@internal Some of the defaults have changed in v1.5, but as the defaults will
		 *            be removed and new defaults will now automatically be passed when no
		 *            data found, this update is automatic (as long as we remove the old
		 *            values which we do in the below routine).}}
		 *
		 * {@internal Unfortunately we can't use the normal delete_meta() with key/value combination
		 *            as '' (empty string) values will be ignored and would result in all metas
		 *            with that key being deleted, not just the empty fields.
		 *            Still, the below implementation is largely based on the delete_meta() function.}}
		 */
		$query = [];

		foreach ( self::$meta_fields as $subset => $field_group ) {
			foreach ( $field_group as $key => $field_def ) {
				if ( ! isset( $field_def['default_value'] ) ) {
					continue;
				}

				if ( isset( $field_def['options'] ) && is_array( $field_def['options'] ) && $field_def['options'] !== [] ) {
					$valid = $field_def['options'];
					// Remove the default value from the valid options.
					unset( $valid[ $field_def['default_value'] ] );
					$valid = array_keys( $valid );

					$query[] = $wpdb->prepare(
						"( meta_key = %s AND meta_value NOT IN ( '" . implode( "','", esc_sql( $valid ) ) . "' ) )",
						self::$meta_prefix . $key
					);
					unset( $valid );
				}
				elseif ( is_string( $field_def['default_value'] ) && $field_def['default_value'] !== '' ) {
					$query[] = $wpdb->prepare(
						'( meta_key = %s AND meta_value = %s )',
						self::$meta_prefix . $key,
						$field_def['default_value']
					);
				}
				else {
					$query[] = $wpdb->prepare(
						"( meta_key = %s AND meta_value = '' )",
						self::$meta_prefix . $key
					);
				}
			}
		}
		unset( $subset, $field_group, $key, $field_def );

		$query    = "SELECT meta_id FROM {$wpdb->postmeta} WHERE " . implode( ' OR ', $query ) . ';';
		$meta_ids = $wpdb->get_col( $query );

		if ( is_array( $meta_ids ) && $meta_ids !== [] ) {
			// WP native action.
			do_action( 'delete_post_meta', $meta_ids, null, null, null );

			$query = "DELETE FROM {$wpdb->postmeta} WHERE meta_id IN( " . implode( ',', $meta_ids ) . ' )';
			$count = $wpdb->query( $query );

			if ( $count ) {
				foreach ( $meta_ids as $object_id ) {
					wp_cache_delete( $object_id, 'post_meta' );
				}

				// WP native action.
				do_action( 'deleted_post_meta', $meta_ids, null, null, null );
			}
		}
		unset( $query, $meta_ids, $count, $object_id );

		/*
		 * Deal with the multiselect (meta-robots-adv) field.
		 *
		 * Removes invalid option combinations, such as 'none,noarchive'.
		 *
		 * Default values have already been removed, so we should have a small result set and
		 * (hopefully) even smaller set of invalid results.
		 */
		$query  = $wpdb->prepare(
			"SELECT meta_id, meta_value FROM {$wpdb->postmeta} WHERE meta_key = %s",
			self::$meta_prefix . 'meta-robots-adv'
		);
		$oldies = $wpdb->get_results( $query );

		if ( is_array( $oldies ) && $oldies !== [] ) {
			foreach ( $oldies as $old ) {
				$clean = self::validate_meta_robots_adv( $old->meta_value );

				if ( $clean !== $old->meta_value ) {
					if ( $clean !== self::$meta_fields['advanced']['meta-robots-adv']['default_value'] ) {
						update_metadata_by_mid( 'post', $old->meta_id, $clean );
					}
					else {
						delete_metadata_by_mid( 'post', $old->meta_id );
					}
				}
			}
		}
		unset( $query, $oldies, $old, $clean );

		do_action( 'wpseo_meta_clean_up' );
	}

	/**
	 * Recursively merge a variable number of arrays, using the left array as base,
	 * giving priority to the right array.
	 *
	 * Difference with native array_merge_recursive():
	 * array_merge_recursive converts values with duplicate keys to arrays rather than
	 * overwriting the value in the first array with the duplicate value in the second array.
	 *
	 * array_merge_recursive_distinct does not change the data types of the values in the arrays.
	 * Matching keys' values in the second array overwrite those in the first array, as is the
	 * case with array_merge.
	 *
	 * Freely based on information found on http://www.php.net/manual/en/function.array-merge-recursive.php
	 *
	 * {@internal Should be moved to a general utility class.}}
	 *
	 * @return array
	 */
	public static function array_merge_recursive_distinct() {

		$arrays = func_get_args();
		if ( count( $arrays ) < 2 ) {
			if ( $arrays === [] ) {
				return [];
			}
			else {
				return $arrays[0];
			}
		}

		$merged = array_shift( $arrays );

		foreach ( $arrays as $array ) {
			foreach ( $array as $key => $value ) {
				if ( is_array( $value ) && ( isset( $merged[ $key ] ) && is_array( $merged[ $key ] ) ) ) {
					$merged[ $key ] = self::array_merge_recursive_distinct( $merged[ $key ], $value );
				}
				else {
					$merged[ $key ] = $value;
				}
			}
			unset( $key, $value );
		}

		return $merged;
	}

	/**
	 * Counts the total of all the keywords being used for posts except the given one.
	 *
	 * @param string $keyword The keyword to be counted.
	 * @param int    $post_id The id of the post to which the keyword belongs.
	 *
	 * @return array
	 */
	public static function keyword_usage( $keyword, $post_id ) {

		if ( empty( $keyword ) ) {
			return [];
		}

		/**
		 * The indexable repository.
		 *
		 * @var Indexable_Repository
		 */
		$repository = YoastSEO()->classes->get( Indexable_Repository::class );

		$post_ids = $repository->query()
			->select( 'object_id' )
			->where( 'primary_focus_keyword', $keyword )
			->where( 'object_type', 'post' )
			->where_not_equal( 'object_id', $post_id )
			->limit( 2 )
			->find_array();

		$callback = static function ( $row ) {
			return (int) $row['object_id'];
		};
		$post_ids = array_map( $callback, $post_ids );

		/*
		 * If Yoast SEO Premium is active, get the additional keywords as well.
		 * We only check for the additional keywords if we've not already found two.
		 * In that case there's no use for an additional query as we already know
		 * that the keyword has been used multiple times before.
		 */
		if ( YoastSEO()->helpers->product->is_premium() && count( $post_ids ) < 2 ) {
			$query = [
				'meta_query'     => [
					[
						'key'     => '_yoast_wpseo_focuskeywords',
						'value'   => sprintf( '"keyword":"%s"', $keyword ),
						'compare' => 'LIKE',
					],
				],
				'post__not_in'   => [ $post_id ],
				'fields'         => 'ids',
				'post_type'      => 'any',

				/*
				 * We only need to return zero, one or two results:
				 * - Zero: keyword hasn't been used before
				 * - One: Keyword has been used once before
				 * - Two or more: Keyword has been used twice or more before
				 */
				'posts_per_page' => 2,
			];
			$get_posts = new WP_Query( $query );
			$post_ids  = array_merge( $post_ids, $get_posts->posts );
		}

		return $post_ids;
	}
}