diff --git a/includes/import/abstract-wc-product-importer.php b/includes/import/abstract-wc-product-importer.php
index 416c1afe326..a09f8908d31 100644
--- a/includes/import/abstract-wc-product-importer.php
+++ b/includes/import/abstract-wc-product-importer.php
@@ -7,6 +7,7 @@
  * @package  WooCommerce/Import
  * @version  3.1.0
  */
+
 if ( ! defined( 'ABSPATH' ) ) {
 	exit;
 }
@@ -15,7 +16,7 @@ if ( ! defined( 'ABSPATH' ) ) {
  * Include dependencies.
  */
 if ( ! class_exists( 'WC_Importer_Interface', false ) ) {
-	include_once( WC_ABSPATH . 'includes/interfaces/class-wc-importer-interface.php' );
+	include_once WC_ABSPATH . 'includes/interfaces/class-wc-importer-interface.php';
 }
 
 /**
@@ -182,11 +183,19 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 			}
 
 			$product = new $classname( $id );
-		} elseif ( isset( $data['id'] ) ) {
+		} elseif ( ! empty( $data['id'] ) ) {
 			$product = wc_get_product( $id );
 
 			if ( ! $product ) {
-				return new WP_Error( 'woocommerce_product_csv_importer_invalid_id', sprintf( __( 'Invalid product ID %d.', 'woocommerce' ), $id ), array( 'id' => $id, 'status' => 401 ) );
+				return new WP_Error(
+					'woocommerce_product_csv_importer_invalid_id',
+					/* translators: %d: product ID */
+					sprintf( __( 'Invalid product ID %d.', 'woocommerce' ), $id ),
+					array(
+						'id'     => $id,
+						'status' => 401,
+					)
+				);
 			}
 		} else {
 			$product = new WC_Product_Simple( $id );
@@ -198,6 +207,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 	/**
 	 * Process a single item and save.
 	 *
+	 * @throws Exception If item cannot be processed.
 	 * @param  array $data Raw CSV data.
 	 * @return array|WC_Error
 	 */
@@ -206,8 +216,12 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 			do_action( 'woocommerce_product_import_before_process_item', $data );
 
 			// Get product ID from SKU if created during the importation.
-			if ( empty( $data['id'] ) && ! empty( $data['sku'] ) && ( $product_id = wc_get_product_id_by_sku( $data['sku'] ) ) ) {
-				$data['id'] = $product_id;
+			if ( empty( $data['id'] ) && ! empty( $data['sku'] ) ) {
+				$product_id = wc_get_product_id_by_sku( $data['sku'] );
+
+				if ( $product_id ) {
+					$data['id'] = $product_id;
+				}
 			}
 
 			$object   = $this->get_product_object( $data );
@@ -301,8 +315,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 	 *
 	 * @param WC_Product $product Product instance.
 	 * @param array      $data    Item data.
-	 *
-	 * @throws Exception
+	 * @throws Exception If data cannot be set.
 	 */
 	protected function set_product_data( &$product, $data ) {
 		if ( isset( $data['raw_attributes'] ) ) {
@@ -338,7 +351,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 					}
 
 					// Check for default attributes and set "is_variation".
-					if ( ! empty( $attribute['default'] ) && in_array( $attribute['default'], $options ) ) {
+					if ( ! empty( $attribute['default'] ) && in_array( $attribute['default'], $options, true ) ) {
 						$default_term = get_term_by( 'name', $attribute['default'], $attribute_name );
 
 						if ( $default_term && ! is_wp_error( $default_term ) ) {
@@ -348,7 +361,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 						}
 
 						$default_attributes[ $attribute_name ] = $default;
-						$is_variation = 1;
+						$is_variation                          = 1;
 					}
 
 					if ( ! empty( $options ) ) {
@@ -363,7 +376,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 					}
 				} elseif ( isset( $attribute['value'] ) ) {
 					// Check for default attributes and set "is_variation".
-					if ( ! empty( $attribute['default'] ) && in_array( $attribute['default'], $attribute['value'] ) ) {
+					if ( ! empty( $attribute['default'] ) && in_array( $attribute['default'], $attribute['value'], true ) ) {
 						$default_attributes[ sanitize_title( $attribute['name'] ) ] = $attribute['default'];
 						$is_variation = 1;
 					}
@@ -392,9 +405,8 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 	 *
 	 * @param WC_Product $variation Product instance.
 	 * @param array      $data    Item data.
-	 *
 	 * @return WC_Product|WP_Error
-	 * @throws Exception
+	 * @throws Exception If data cannot be set.
 	 */
 	protected function set_variation_data( &$variation, $data ) {
 		$parent = false;
@@ -506,6 +518,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 	 * @param  string $url        Attachment URL.
 	 * @param  int    $product_id Product ID.
 	 * @return int
+	 * @throws Exception If attachment cannot be loaded.
 	 */
 	public function get_attachment_id_from_url( $url, $product_id ) {
 		if ( empty( $url ) ) {
@@ -524,7 +537,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 				'post_type'   => 'attachment',
 				'post_status' => 'any',
 				'fields'      => 'ids',
-				'meta_query'  => array(
+				'meta_query'  => array( // @codingStandardsIgnoreLine.
 					'relation' => 'OR',
 					array(
 						'key'     => '_wp_attached_file',
@@ -549,7 +562,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 				'post_type'   => 'attachment',
 				'post_status' => 'any',
 				'fields'      => 'ids',
-				'meta_query'  => array(
+				'meta_query'  => array( // @codingStandardsIgnoreLine.
 					array(
 						'value' => $url,
 						'key'   => '_wc_attachment_source',
@@ -558,7 +571,9 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 			);
 		}
 
-		if ( $ids = get_posts( $args ) ) {
+		$ids = get_posts( $args ); // @codingStandardsIgnoreLine.
+
+		if ( $ids ) {
 			$id = current( $ids );
 		}
 
@@ -573,6 +588,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 			$id = wc_rest_set_uploaded_image_as_attachment( $upload, $product_id );
 
 			if ( ! wp_attachment_is_image( $id ) ) {
+				/* translators: %s: image URL */
 				throw new Exception( sprintf( __( 'Not able to attach "%s".', 'woocommerce' ), $url ), 400 );
 			}
 
@@ -581,6 +597,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 		}
 
 		if ( ! $id ) {
+			/* translators: %s: image URL */
 			throw new Exception( sprintf( __( 'Unable to use image "%s".', 'woocommerce' ), $url ), 400 );
 		}
 
@@ -593,20 +610,23 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 	 *
 	 * @param  string $raw_name Attribute name.
 	 * @return int
+	 * @throws Exception If taxonomy cannot be loaded.
 	 */
 	public function get_attribute_taxonomy_id( $raw_name ) {
 		global $wpdb, $wc_product_attributes;
 
 		// These are exported as labels, so convert the label to a name if possible first.
 		$attribute_labels = wp_list_pluck( wc_get_attribute_taxonomies(), 'attribute_label', 'attribute_name' );
-		$attribute_name   = '';
+		$attribute_name   = array_search( $raw_name, $attribute_labels, true );
 
-		if ( ! $attribute_name = array_search( $raw_name, $attribute_labels ) ) {
+		if ( ! $attribute_name ) {
 			$attribute_name = wc_sanitize_taxonomy_name( $raw_name );
 		}
 
+		$attribute_id = wc_attribute_taxonomy_id_by_name( $attribute_name );
+
 		// Get the ID from the name.
-		if ( $attribute_id = wc_attribute_taxonomy_id_by_name( $attribute_name ) ) {
+		if ( $attribute_id ) {
 			return $attribute_id;
 		}
 
@@ -709,7 +729,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 	 * separators.
 	 *
 	 * @since  3.2.0
-	 * @param  string $value
+	 * @param  string $value Value to explode.
 	 * @return array
 	 */
 	protected function explode_values( $value ) {
@@ -724,7 +744,7 @@ abstract class WC_Product_Importer implements WC_Importer_Interface {
 	 * Remove formatting and trim each value.
 	 *
 	 * @since  3.2.0
-	 * @param  string $value
+	 * @param  string $value Value to format.
 	 * @return string
 	 */
 	protected function explode_values_formatter( $value ) {