diff --git a/includes/ContentImport/ImportLogger.php b/includes/ContentImport/ImportLogger.php
index 64817834..045c2234 100644
--- a/includes/ContentImport/ImportLogger.php
+++ b/includes/ContentImport/ImportLogger.php
@@ -7,9 +7,12 @@
 
 class ImportLogger {
 
-	protected $levels_delimiter = '/';
+	protected string $levels_delimiter = '/';
 
-	protected $data = array(
+	/**
+	 * @var array<string, array>
+	 */
+	protected array $data = array(
 		'info'    => array(),
 		'error'   => array(),
 		'success' => array(),
@@ -29,7 +32,7 @@ public function __construct( ImportCoordinates $import_coordinates ) {
 	 *
 	 * @param ImportLogger|null $logger
 	 */
-	public function merge( ImportLogger $logger = null ) {
+	public function merge( ImportLogger $logger = null ): void {
 		if ( null === $logger ) {
 			return;
 		}
@@ -38,16 +41,16 @@ public function merge( ImportLogger $logger = null ) {
 	}
 
 	/**
-	 * @return array
+	 * @return array<string, array>
 	 */
-	public function get_data() {
+	public function get_data(): array {
 		return $this->data;
 	}
 
 	/**
 	 * Saves the log or prints it some place.
 	 */
-	public function save() {
+	public function save(): void {
 		$log_writer = $default_log_writer = AdminNoticeLogger::instance();
 		$log_writer->set_import_coordinates( $this->import_coordinates );
 
@@ -82,7 +85,7 @@ public function save() {
 	 * @param string $where A location string using `/` as level format.
 	 * @param mixed  $what What should be stored in the log.
 	 */
-	public function log_error( $where, $what ) {
+	public function log_error( $where, $what ): void {
 		$this->log( $where, $what, 'error' );
 	}
 
@@ -93,7 +96,7 @@ public function log_error( $where, $what ) {
 	 * @param mixed  $what What should be stored in the log.
 	 * @param string $root Where to log the information.
 	 */
-	protected function log( $where, $what, $root = 'info' ) {
+	protected function log( $where, $what, $root = 'info' ): void {
 		if ( ! isset( $this->data[ $root ] ) ) {
 			$this->data[ $root ] = array();
 		}
@@ -103,7 +106,7 @@ protected function log( $where, $what, $root = 'info' ) {
 		$this->data[ $root ] = array_merge_recursive( $this->data[ $root ], $data );
 	}
 
-	protected function build_nested_array( $path, $what = '' ) {
+	protected function build_nested_array( $path, $what = '' ): array {
 		$json = '{"'
 				. implode( '":{"', $path )
 				. '":' . wp_json_encode( $what )
@@ -125,7 +128,7 @@ protected function build_nested_array( $path, $what = '' ) {
 	 *
 	 * @return array
 	 */
-	protected function build_path( $where ) {
+	protected function build_path( $where ): array {
 		$where_path = explode( $this->levels_delimiter, $where );
 
 		return $where_path;
@@ -136,7 +139,7 @@ protected function build_path( $where ) {
 	 *
 	 * @return string
 	 */
-	public function get_levels_delimiter() {
+	public function get_levels_delimiter(): string {
 		return $this->levels_delimiter;
 	}
 
@@ -145,7 +148,7 @@ public function get_levels_delimiter() {
 	 *
 	 * @param string $levels_delimiter
 	 */
-	public function set_levels_delimiter( $levels_delimiter ) {
+	public function set_levels_delimiter( $levels_delimiter ): void {
 		$this->levels_delimiter = $levels_delimiter;
 	}
 
@@ -155,7 +158,7 @@ public function set_levels_delimiter( $levels_delimiter ) {
 	 * @param string $where A location string using `/` as level format.
 	 * @param mixed  $what What should be stored in the log.
 	 */
-	public function log_success( $where, $what ) {
+	public function log_success( $where, $what ): void {
 		$this->log( $where, $what, 'success' );
 	}
 
@@ -164,16 +167,21 @@ public function log_success( $where, $what ) {
 	 *
 	 * @param string $message
 	 */
-	public function log_information( $key, $message ) {
+	public function log_information( $key, $message ): void {
 		$this->data['info'][ $key ] = $message;
 	}
 
+	/**
+	 * @param string $where
+	 *
+	 * @return mixed
+	 */
 	public function get_error( $where ) {
 		return $this->get_nested_value( 'error' . $this->levels_delimiter . $where );
 	}
 
 	/**
-	 * @param $where
+	 * @param string $where
 	 *
 	 * @return mixed
 	 */
@@ -189,10 +197,20 @@ protected function get_nested_value( $where ) {
 		return $data;
 	}
 
+	/**
+	 * @param string $where
+	 *
+	 * @return mixed
+	 */
 	public function get_success( $where ) {
 		return $this->get_nested_value( 'success' . $this->levels_delimiter . $where );
 	}
 
+	/**
+	 * @param string $key
+	 *
+	 * @return mixed
+	 */
 	public function get_information( $key ) {
 		return isset( $this->data['info'][ $key ] ) ? $this->data['info'][ $key ] : '';
 	}
diff --git a/includes/ContentImport/Importers/AttachmentsImporters.php b/includes/ContentImport/Importers/AttachmentsImporters.php
index fc5d1816..f1f33399 100644
--- a/includes/ContentImport/Importers/AttachmentsImporters.php
+++ b/includes/ContentImport/Importers/AttachmentsImporters.php
@@ -8,21 +8,24 @@ class AttachmentsImporters extends ImportersBaseFactory {
 
 	const TYPE = 'attachments';
 
-	protected $importers_map = [
+	/**
+	 * @var array<string, string>
+	 */
+	protected array $importers_map = array(
 		Linking::TYPE => Linking::class,
-	];
+	);
 
 	/**
 	 * Returns the factory details.
 	 *
-	 * @return string
+	 * @return \stdClass
 	 */
 	public function details() {
-		return (object) [
+		return (object) array(
 			'slug'      => static::TYPE,
 			'name'      => __( 'Image Attachments', 'multisite-language-switcher' ),
 			'importers' => $this->importers_info(),
 			'selected'  => $this->selected(),
-		];
+		);
 	}
 }
diff --git a/includes/ContentImport/Importers/ImportersBaseFactory.php b/includes/ContentImport/Importers/ImportersBaseFactory.php
index 70efb1f0..e2b4ff19 100644
--- a/includes/ContentImport/Importers/ImportersBaseFactory.php
+++ b/includes/ContentImport/Importers/ImportersBaseFactory.php
@@ -13,10 +13,10 @@ abstract class ImportersBaseFactory extends MslsRegistryInstance implements Impo
 	const TYPE = 'none';
 
 	/**
-	 * @var array An array defining the slug and Importer class relationships in
+	 * @var array<string, string> An array defining the slug and Importer class relationships in
 	 *            the shape [ <slug> => <importer-class> ]
 	 */
-	protected $importers_map = [];
+	protected array $importers_map = array();
 
 	/**
 	 * @return Importer
@@ -49,7 +49,6 @@ public function make( ImportCoordinates $import_coordinates ) {
 		 * @param ImportCoordinates $import_coordinates
 		 *
 		 * @since TBD
-		 *
 		 */
 		$map = apply_filters( "msls_content_import_{$type}_importers_map", $this->importers_map, $import_coordinates );
 
@@ -70,10 +69,10 @@ public function make( ImportCoordinates $import_coordinates ) {
 	 * @return \stdClass
 	 */
 	public function details() {
-		return (object) [
+		return (object) array(
 			'name'      => 'Base Factory',
-			'importers' => [],
-		];
+			'importers' => array(),
+		);
 	}
 
 	/**
@@ -90,9 +89,6 @@ public function selected() {
 		 *
 		 * @param string $selected The selected importer slug.
 		 * @param ImportersFactory $this
-		 *
-		 * @since TBD
-		 *
 		 */
 		$selected = apply_filters( "msls_content_import_{$slug}_selected", $selected, $this );
 
@@ -102,9 +98,12 @@ public function selected() {
 	protected function importers_info() {
 		return array_combine(
 			array_keys( $this->importers_map ),
-			array_map( function ( $importer_class ) {
-				return $importer_class::info();
-			}, $this->importers_map )
+			array_map(
+				function ( $importer_class ) {
+					return $importer_class::info();
+				},
+				$this->importers_map
+			)
 		);
 	}
-}
\ No newline at end of file
+}
diff --git a/includes/ContentImport/Importers/ImportersFactory.php b/includes/ContentImport/Importers/ImportersFactory.php
index 086f6a04..3735b4f7 100644
--- a/includes/ContentImport/Importers/ImportersFactory.php
+++ b/includes/ContentImport/Importers/ImportersFactory.php
@@ -18,7 +18,7 @@ public function make( ImportCoordinates $import_coordinates );
 	/**
 	 * Returns the factory details.
 	 *
-	 * @return string
+	 * @return \stdClass
 	 */
 	public function details();
 
@@ -28,4 +28,4 @@ public function details();
 	 * @return string
 	 */
 	public function selected();
-}
\ No newline at end of file
+}
diff --git a/includes/ContentImport/Importers/PostFieldsImporters.php b/includes/ContentImport/Importers/PostFieldsImporters.php
index 1f1aa41e..2e0d989e 100644
--- a/includes/ContentImport/Importers/PostFieldsImporters.php
+++ b/includes/ContentImport/Importers/PostFieldsImporters.php
@@ -8,21 +8,24 @@ class PostFieldsImporters extends ImportersBaseFactory {
 
 	const TYPE = 'post-fields';
 
-	protected $importers_map = [
+	/**
+	 * @var array<string, string>
+	 */
+	protected array $importers_map = array(
 		Duplicating::TYPE => Duplicating::class,
-	];
+	);
 
 	/**
 	 * Returns the factory details.
 	 *
-	 * @return string
+	 * @return \stdClass
 	 */
 	public function details() {
-		return (object) [
+		return (object) array(
 			'slug'      => static::TYPE,
 			'name'      => __( 'Post Fields', 'multisite-language-switcher' ),
 			'importers' => $this->importers_info(),
 			'selected'  => $this->selected(),
-		];
+		);
 	}
 }
diff --git a/includes/ContentImport/Importers/PostMeta/Duplicating.php b/includes/ContentImport/Importers/PostMeta/Duplicating.php
index 356248e6..fbdc7c37 100644
--- a/includes/ContentImport/Importers/PostMeta/Duplicating.php
+++ b/includes/ContentImport/Importers/PostMeta/Duplicating.php
@@ -2,6 +2,7 @@
 
 namespace lloc\Msls\ContentImport\Importers\PostMeta;
 
+use lloc\Msls\ContentImport\ImportCoordinates;
 use lloc\Msls\ContentImport\Importers\BaseImporter;
 
 class Duplicating extends BaseImporter {
@@ -14,11 +15,11 @@ class Duplicating extends BaseImporter {
 	 * @return \stdClass
 	 */
 	public static function info() {
-		return (object) [
-			'slug' => static::TYPE,
-			'name' => __( 'Duplicating', 'multisite-language-switcher' ),
-			'description' => __( 'Copies the source post meta to the destination.', 'multisite-language-switcher' )
-		];
+		return (object) array(
+			'slug'        => static::TYPE,
+			'name'        => __( 'Duplicating', 'multisite-language-switcher' ),
+			'description' => __( 'Copies the source post meta to the destination.', 'multisite-language-switcher' ),
+		);
 	}
 
 	public function import( array $data ) {
@@ -49,6 +50,13 @@ public function import( array $data ) {
 		return $data;
 	}
 
+	/**
+	 * Filters the post meta that should not be imported.
+	 *
+	 * @param array $meta
+	 *
+	 * @return array
+	 */
 	public function filter_post_meta( array $meta ) {
 		$blacklist = array( '_edit_last', '_thumbnail_id', '_edit_lock' );
 
@@ -59,11 +67,13 @@ public function filter_post_meta( array $meta ) {
 		 * @param array $meta
 		 * @param ImportCoordinates $import_coordinates
 		 */
-		$blacklist = apply_filters( 'msls_content_import_post_meta_blacklist',
+		$blacklist = apply_filters(
+			'msls_content_import_post_meta_blacklist',
 			$blacklist,
 			$meta,
-			$this->import_coordinates );
+			$this->import_coordinates
+		);
 
 		return array_diff_key( $meta, array_combine( $blacklist, $blacklist ) );
 	}
-}
\ No newline at end of file
+}
diff --git a/includes/ContentImport/Importers/PostMetaImporters.php b/includes/ContentImport/Importers/PostMetaImporters.php
index da6d2315..8930ff9d 100644
--- a/includes/ContentImport/Importers/PostMetaImporters.php
+++ b/includes/ContentImport/Importers/PostMetaImporters.php
@@ -8,21 +8,24 @@ class PostMetaImporters extends ImportersBaseFactory {
 
 	const TYPE = 'post-meta';
 
-	protected $importers_map = [
+	/**
+	 * @var array<string, string>
+	 */
+	protected array $importers_map = array(
 		Duplicating::TYPE => Duplicating::class,
-	];
+	);
 
 	/**
 	 * Returns the factory details.
 	 *
-	 * @return string
+	 * @return \stdClass
 	 */
 	public function details() {
-		return (object) [
+		return (object) array(
 			'slug'      => static::TYPE,
 			'name'      => __( 'Meta Fields', 'multisite-language-switcher' ),
 			'importers' => $this->importers_info(),
 			'selected'  => $this->selected(),
-		];
+		);
 	}
 }
diff --git a/includes/ContentImport/Importers/PostThumbnail/Linking.php b/includes/ContentImport/Importers/PostThumbnail/Linking.php
index ec9c4820..32cbdcdd 100644
--- a/includes/ContentImport/Importers/PostThumbnail/Linking.php
+++ b/includes/ContentImport/Importers/PostThumbnail/Linking.php
@@ -22,12 +22,14 @@ class Linking extends BaseImporter {
 	 * @return \stdClass
 	 */
 	public static function info() {
-		return (object) [
+		return (object) array(
 			'slug'        => static::TYPE,
 			'name'        => __( 'Linking', 'multisite-language-switcher' ),
-			'description' => __( 'Links the featured image from the source post to the destination post; the image is not duplicated.',
-				'multisite-language-switcher' )
-		];
+			'description' => __(
+				'Links the featured image from the source post to the destination post; the image is not duplicated.',
+				'multisite-language-switcher'
+			),
+		);
 	}
 
 	public function import( array $data ) {
@@ -55,12 +57,19 @@ public function import( array $data ) {
 
 		if ( $source_post_thumbnail_attachment instanceof \WP_Post ) {
 			// in some instances the folder sep. `/` might be duplicated, we de-duplicate it
-			array_walk( $source_upload_dir, function ( &$entry ) {
-				$entry = str_replace( '//', '/', $entry );
-			} );
-			$source_uploads_dir         = untrailingslashit( str_replace( $source_upload_dir['subdir'],
-				'',
-				$source_upload_dir['path'] ) );
+			array_walk(
+				$source_upload_dir,
+				function ( &$entry ) {
+					$entry = str_replace( '//', '/', $entry );
+				}
+			);
+			$source_uploads_dir         = untrailingslashit(
+				str_replace(
+					$source_upload_dir['subdir'],
+					'',
+					$source_upload_dir['path']
+				)
+			);
 			$source_post_thumbnail_file = $source_uploads_dir . '/' . $source_post_thumbnail_meta['_wp_attached_file'];
 
 			// Check the type of file. We'll use this as the 'post_mime_type'.
@@ -75,10 +84,10 @@ public function import( array $data ) {
 				'post_status'    => 'inherit',
 			);
 
-			$existing_criteria = [
+			$existing_criteria = array(
 				'post_type' => 'attachment',
 				'title'     => $attachment['post_title'],
-			];
+			);
 
 			$found = get_posts( $existing_criteria );
 
@@ -87,9 +96,11 @@ public function import( array $data ) {
 				$this->logger->log_success( 'post-thumbnail/existing', $dest_post_thumbnail_id );
 			} else {
 				// Insert the attachment.
-				$dest_post_thumbnail_id = wp_insert_attachment( $attachment,
+				$dest_post_thumbnail_id = wp_insert_attachment(
+					$attachment,
 					$source_post_thumbnail_file,
-					$dest_post_id );
+					$dest_post_id
+				);
 
 				if ( empty( $dest_post_thumbnail_id ) ) {
 					$this->logger->log_error( 'post-thumbnail/created', $dest_post_thumbnail_id );
@@ -105,10 +116,14 @@ public function import( array $data ) {
 				}
 			}
 
-			update_post_meta( $dest_post_thumbnail_id, AttachmentPathFinder::LINKED, [
-				'blog' => $source_blog_id,
-				'post' => $source_post_thumbnail_id
-			] );
+			update_post_meta(
+				$dest_post_thumbnail_id,
+				AttachmentPathFinder::LINKED,
+				array(
+					'blog' => $source_blog_id,
+					'post' => $source_post_thumbnail_id,
+				)
+			);
 
 			$dest_post_thumbnail_set = set_post_thumbnail( $dest_post_id, $dest_post_thumbnail_id );
 
@@ -124,11 +139,22 @@ public function import( array $data ) {
 		return $data;
 	}
 
+	/**
+	 * @param int $source_post_thumbnail_id
+	 *
+	 * @return array
+	 */
 	protected function get_attachment_meta( $source_post_thumbnail_id ) {
-		$keys = [ '_wp_attached_file', '_wp_attachment_metadata', '_wp_attachment_image_alt' ];
-
-		return array_combine( $keys, array_map( function ( $key ) use ( $source_post_thumbnail_id ) {
-			return get_post_meta( $source_post_thumbnail_id, $key, true );
-		}, $keys ) );
+		$keys = array( '_wp_attached_file', '_wp_attachment_metadata', '_wp_attachment_image_alt' );
+
+		return array_combine(
+			$keys,
+			array_map(
+				function ( $key ) use ( $source_post_thumbnail_id ) {
+					return get_post_meta( $source_post_thumbnail_id, $key, true );
+				},
+				$keys
+			)
+		);
 	}
-}
\ No newline at end of file
+}
diff --git a/includes/ContentImport/Importers/PostThumbnailImporters.php b/includes/ContentImport/Importers/PostThumbnailImporters.php
index 8668defe..d1cb0716 100644
--- a/includes/ContentImport/Importers/PostThumbnailImporters.php
+++ b/includes/ContentImport/Importers/PostThumbnailImporters.php
@@ -8,21 +8,24 @@ class PostThumbnailImporters extends ImportersBaseFactory {
 
 	const TYPE = 'post-thumbnail';
 
-	protected $importers_map = [
+	/**
+	 * @var array<string, string>
+	 */
+	protected array $importers_map = array(
 		Linking::TYPE => Linking::class,
-	];
+	);
 
 	/**
 	 * Returns the factory details.
 	 *
-	 * @return string
+	 * @return \stdClass
 	 */
 	public function details() {
-		return (object) [
+		return (object) array(
 			'slug'      => static::TYPE,
 			'name'      => __( 'Featured Image', 'multisite-language-switcher' ),
 			'importers' => $this->importers_info(),
 			'selected'  => $this->selected(),
-		];
+		);
 	}
 }
diff --git a/includes/ContentImport/Importers/Terms/ShallowDuplicating.php b/includes/ContentImport/Importers/Terms/ShallowDuplicating.php
index e35520c0..2b70d0c6 100644
--- a/includes/ContentImport/Importers/Terms/ShallowDuplicating.php
+++ b/includes/ContentImport/Importers/Terms/ShallowDuplicating.php
@@ -2,6 +2,7 @@
 
 namespace lloc\Msls\ContentImport\Importers\Terms;
 
+use lloc\Msls\ContentImport\ImportCoordinates;
 use lloc\Msls\ContentImport\Importers\BaseImporter;
 use lloc\Msls\MslsOptionsTax;
 use lloc\Msls\MslsOptionsTaxTerm;
@@ -95,6 +96,13 @@ public function import( array $data ) {
 		return $data;
 	}
 
+	/**
+	 * @param \WP_Term           $term
+	 * @param MslsOptionsTaxTerm $msls_term
+	 * @param string             $dest_lang
+	 *
+	 * @return bool|int
+	 */
 	protected function create_local_term( \WP_Term $term, MslsOptionsTax $msls_term, $dest_lang ) {
 		$meta         = get_term_meta( $term->term_id );
 		$dest_term_id = wp_create_term( $term->name, $term->taxonomy );
@@ -118,6 +126,12 @@ protected function create_local_term( \WP_Term $term, MslsOptionsTax $msls_term,
 		return $dest_term_id;
 	}
 
+	/**
+	 * @param array    $meta
+	 * @param \WP_Term $term
+	 *
+	 * @return array
+	 */
 	protected function filter_term_meta( array $meta, \WP_Term $term ) {
 		/**
 		 * Filters the list of term meta that should not be imported for a term.
@@ -138,6 +152,13 @@ protected function filter_term_meta( array $meta, \WP_Term $term ) {
 		return array_diff_key( $meta, array_combine( $blacklist, $blacklist ) );
 	}
 
+	/**
+	 * @param int    $object_id
+	 * @param int    $dest_term_id
+	 * @param string $taxonomy
+	 *
+	 * @return array|\WP_Error
+	 */
 	protected function update_object_terms( $object_id, $dest_term_id, $taxonomy ) {
 		if ( ! in_array( $taxonomy, $this->reset_taxonomies, true ) ) {
 			wp_set_object_terms( $object_id, array(), $taxonomy );
diff --git a/includes/ContentImport/Importers/TermsImporters.php b/includes/ContentImport/Importers/TermsImporters.php
index 9ed1a68c..21b7d86d 100644
--- a/includes/ContentImport/Importers/TermsImporters.php
+++ b/includes/ContentImport/Importers/TermsImporters.php
@@ -8,21 +8,24 @@ class TermsImporters extends ImportersBaseFactory {
 
 	const TYPE = 'terms';
 
-	protected $importers_map = [
+	/**
+	 * @var array<string, string>
+	 */
+	protected array $importers_map = array(
 		ShallowDuplicating::TYPE => ShallowDuplicating::class,
-	];
+	);
 
 	/**
 	 * Returns the factory details.
 	 *
-	 * @return string
+	 * @return \stdClass
 	 */
 	public function details() {
-		return (object) [
+		return (object) array(
 			'slug'      => static::TYPE,
 			'name'      => __( 'Taxonomy Terms', 'multisite-language-switcher' ),
 			'importers' => $this->importers_info(),
 			'selected'  => $this->selected(),
-		];
+		);
 	}
 }
diff --git a/includes/ContentImport/LogWriters/AdminNoticeLogger.php b/includes/ContentImport/LogWriters/AdminNoticeLogger.php
index dd11d0fa..15966ee8 100644
--- a/includes/ContentImport/LogWriters/AdminNoticeLogger.php
+++ b/includes/ContentImport/LogWriters/AdminNoticeLogger.php
@@ -6,7 +6,8 @@
 use lloc\Msls\MslsRegistryInstance;
 
 class AdminNoticeLogger extends MslsRegistryInstance implements LogWriter {
-	protected $transient = 'msls_last_import_log';
+
+	protected string $transient = 'msls_last_import_log';
 
 	/**
 	 * @var ImportCoordinates
@@ -105,7 +106,14 @@ public function write( array $data ) {
 		set_transient( $this->transient, $html, HOUR_IN_SECONDS );
 	}
 
-	protected function get_section_html( $section_title, $entries, $escape_entries = true ) {
+	/**
+	 * @param string $section_title
+	 * @param array  $entries
+	 * @param bool   $escape_entries
+	 *
+	 * @return string
+	 */
+	protected function get_section_html( $section_title, $entries, $escape_entries = true ): string {
 		$html  = '<h3>' . $section_title . '</h3>';
 		$html .= '<ul>';
 		foreach ( $entries as $entry ) {
@@ -120,9 +128,16 @@ protected function get_section_html( $section_title, $entries, $escape_entries =
 		return $html;
 	}
 
-	public function show_last_log( $echo = true ) {
+	/**
+	 * Shows the last log that was written.
+	 *
+	 * @param bool $echo
+	 *
+	 * @return ?string
+	 */
+	public function show_last_log( $echo = true ): ?string {
 		if ( ! ( $html = get_transient( $this->transient ) ) ) {
-			return;
+			return null;
 		}
 
 		if ( $echo ) {
@@ -135,7 +150,10 @@ public function show_last_log( $echo = true ) {
 		return $html;
 	}
 
-	public function set_import_coordinates( $import_coordinates ) {
+	/**
+	 * @param ImportCoordinates $import_coordinates
+	 */
+	public function set_import_coordinates( $import_coordinates ): void {
 		$this->import_coordinates = $import_coordinates;
 	}
 
@@ -144,7 +162,7 @@ public function set_import_coordinates( $import_coordinates ) {
 	 *
 	 * @return string
 	 */
-	public function get_transient() {
+	public function get_transient(): string {
 		return $this->transient;
 	}
 }
diff --git a/includes/ContentImport/MetaBox.php b/includes/ContentImport/MetaBox.php
index f37e7361..01791a19 100644
--- a/includes/ContentImport/MetaBox.php
+++ b/includes/ContentImport/MetaBox.php
@@ -18,7 +18,7 @@ class MetaBox extends MslsRegistryInstance {
 	/**
 	 * Renders the content import metabox.
 	 */
-	public function render() {
+	public function render(): void {
 		$post            = get_post();
 		$mydata          = new MslsOptionsPost( $post->ID );
 		$languages       = MslsOptionsPost::instance()->get_available_languages();
@@ -83,7 +83,7 @@ function ( $lang ) use ( $mydata ) {
 		echo $output;
 	}
 
-	protected function inline_thickbox_url( array $data = array() ) {
+	protected function inline_thickbox_url( array $data = array() ): string {
 		$args = array_merge(
 			array(
 				'modal'    => true,
@@ -99,11 +99,11 @@ protected function inline_thickbox_url( array $data = array() ) {
 		);
 	}
 
-	public function print_modal_html() {
+	public function print_modal_html(): void {
 		echo $this->inline_thickbox_html( true, $this->data );
 	}
 
-	protected function inline_thickbox_html( $echo = true, array $data = array() ) {
+	protected function inline_thickbox_html( $echo = true, array $data = array() ): string {
 		if ( ! isset( $data['msls_import'] ) ) {
 			return '';
 		}
diff --git a/includes/ContentImport/Relations.php b/includes/ContentImport/Relations.php
index 06abeebe..c7bcea1e 100644
--- a/includes/ContentImport/Relations.php
+++ b/includes/ContentImport/Relations.php
@@ -13,15 +13,9 @@
  */
 class Relations {
 
-	/**
-	 * @var MslsOptions[]
-	 */
-	public $to_create = [];
+	public array $to_create = array();
 
-	/**
-	 * @var MslsOptions[]
-	 */
-	protected $local_options = [];
+	protected array $local_options = array();
 
 	/**
 	 * @var ImportCoordinates
@@ -42,7 +36,7 @@ public function __construct( ImportCoordinates $import_coordinates ) {
 	 *
 	 * @param Relations|null $relations
 	 */
-	public function merge( Relations $relations = null ) {
+	public function merge( Relations $relations = null ): void {
 		if ( null === $relations ) {
 			return;
 		}
@@ -53,36 +47,35 @@ public function merge( Relations $relations = null ) {
 	/**
 	 * @return array
 	 */
-	public function get_data() {
+	public function get_data(): array {
 		return $this->to_create;
 	}
 
 	/**
 	 * Creates the relations between the source blog elements and the destination one.
 	 */
-	public function create() {
+	public function create(): void {
 		$this->create_source_to_local();
 		$this->create_local_to_source();
 		restore_current_blog();
 	}
 
-	protected function create_source_to_local() {
+	protected function create_source_to_local(): void {
 		switch_to_blog( $this->import_coordinates->source_blog_id );
 
 		foreach ( $this->to_create as $relation ) {
 			/** @var MslsOptions $option */
 			list( $option, $lang, $id ) = $relation;
-			$option->save( [ $lang => $id ] );
+			$option->save( array( $lang => $id ) );
 			$source_id = $option->get_arg( 0, $id );
 
-			$this->local_options[ $source_id ] = [ $option, $id ];
+			$this->local_options[ $source_id ] = array( $option, $id );
 		}
 	}
 
-	protected function create_local_to_source() {
+	protected function create_local_to_source(): void {
 		switch_to_blog( $this->import_coordinates->dest_blog_id );
 
-		/** @var MslsOptions $local_option */
 		foreach ( $this->local_options as $source_id => $option_data ) {
 			list( $source_option, $local_id ) = $option_data;
 
@@ -94,18 +87,20 @@ protected function create_local_to_source() {
 			 * @param int $source_id
 			 * @param MslsOptions $source_option
 			 */
-			$created = apply_filters( 'msls_content_import_relation_local_to_source_create',
+			$created = apply_filters(
+				'msls_content_import_relation_local_to_source_create',
 				null,
 				$local_id,
 				$source_id,
-				$source_option );
+				$source_option
+			);
 			if ( null !== $created ) {
 				continue;
 			}
 
 			$option_class = get_class( $source_option );
-			$local_option = call_user_func( [ $option_class, 'create' ], $local_id );
-			$local_option->save( [ $this->import_coordinates->source_lang => $source_id ] );
+			$local_option = call_user_func( array( $option_class, 'create' ), $local_id );
+			$local_option->save( array( $this->import_coordinates->source_lang => $source_id ) );
 		}
 	}
 
@@ -113,10 +108,10 @@ protected function create_local_to_source() {
 	 * Sets a relation that should be created.
 	 *
 	 * @param MslsOptions $creator
-	 * @param string $dest_lang
-	 * @param string $dest_post_id
+	 * @param string      $dest_lang
+	 * @param string      $dest_post_id
 	 */
-	public function should_create( MslsOptions $creator, $dest_lang, $dest_post_id ) {
-		$this->to_create[] = [ $creator, $dest_lang, $dest_post_id ];
+	public function should_create( MslsOptions $creator, $dest_lang, $dest_post_id ): void {
+		$this->to_create[] = array( $creator, $dest_lang, $dest_post_id );
 	}
-}
\ No newline at end of file
+}