woocommerce product variation importer - two columns required: post_parent and sku.

import.php

<?php

if ( $_SERVER['HTTP_HOST'] != 'localhost' ) {
	die( 'Only locally enabled! change import-csv.php.' );
}

$csv = filter_input( INPUT_GET, 'csv' );
if ( ! $csv ) {
	?>
	<form>
		<p>
			<label>
				<select name="csv" required>
					CSV file
					<option value="" disabled>Kies</option>
					<?php
					if ( $csv_files = glob( 'csv/*.csv' ) ) {
						foreach ( $csv_files as $file ) {
							echo '<option>', $file, '</option>';
						}
					}?>
				</select>
			</label>
		</p>
		<button>Import variations</button>
	</form>
	<?php
	die;
}

if ( $fh = fopen( $csv, 'r' ) ) {
	include 'wp-load.php';

	set_time_limit( 0 );
	error_reporting( - 1 );
	ini_set( 'display_errors', 'On' );
	$columns = null;
	while ( ob_get_level() ) {
		ob_end_flush();
	}
	ob_implicit_flush( true );

	//http://woothemes.github.io/woocommerce-rest-api-docs/#products-properties
	$editable_meta = array(
		//If the variation is downloadable or not. Downloadable variations give access to a file upon purchase
		'downloadable'          => 'boolean',
		//If the variation is virtual or not. Virtual variations are intangible and aren’t shipped
		'virtual'               => 'boolean',
		//SKU refers to a Stock-keeping unit, a unique identifier for each distinct product and service that can be purchased
		'sku'                   => 'string',
		//Variation regular price
		'regular_price'         => 'float',
		//Variation sale price
		'sale_price'            => 'float',
		//Sets the sale start date. Date in the YYYY-MM-DD format WRITE-ONLY
		'sale_price_dates_from' => 'float',
		//Sets the sale end date. Date in the YYYY-MM-DD format WRITE-ONLY
		'sale_price_dates_to'   => 'float',
		//Tax status. The options are: taxable, shipping (Shipping only) and none
		'tax_status'            => 'string',
		//Tax class
		'tax_class'             => 'string',
		//Enable stock management at variation level
		'managing_stock'        => 'boolean',
		//Stock quantity. If is a variable variation this value will be used to control stock for all variations, unless you define stock at variation level.
		'stock_quantity'        => 'integer',
		//Controls whether or not the variation is listed as “in stock” or “out of stock” on the frontend.
		'in_stock'              => 'boolean',
		//Variation weight in decimal format
		'weight'                => 'string',
		//List of the variation dimensions. See Dimensions Properties
		'dimensions'            => 'array',
		//Shipping class slug. Shipping classes are used by certain shipping methods to group similar products
		'shipping_class'        => 'string',
		//Variation featured image. See Images Properties
		'images'                => 'array',
		//List of variation attributes. Similar to a simple or variable product, but for variation indicate the attributes used to form the variation. See Attributes Properties
		'attributes'            => 'array',
		//List of downloadable files. See Downloads Properties
		'downloads'             => 'array',
		//Amount of times the variation can be downloaded. In write-mode you can sent a blank string for unlimited re-downloads. e.g ''
		'download_limit'        => 'integer',
		//Number of days that the customer has up to be able to download the varition. In write-mode you can sent a blank string for never expiry. e.g ''
		'download_expiry'       => 'integer',
	);

	$str2number = function ( $str ) {
		$number_unformat = function ( $number, $force_number = true, $dec_point = '.', $thousands_sep = ',' ) {
			if ( $force_number ) {
				$number = preg_replace( '/^[^\d]+/', '', $number );
			} else if ( preg_match( '/^[^\d]+/', $number ) ) {
				return false;
			}
			$type   = ( strpos( $number, $dec_point ) === false ) ? 'int' : 'float';
			$number = str_replace( array( $dec_point, $thousands_sep ), array( '.', '' ), $number );
			settype( $number, $type );

			return $number;
		};

		// 0 -9, . and ,
		$str = preg_replace( '@[^\d,\.]+@', '', $str );

		$point_pos = strpos( $str, '.' );
		$comma_pos = strpos( $str, ',' );
		// both comma and point found, and comma is later then point (comma as decimal seperator);
		if ( $point_pos && $comma_pos ) {
			return $number_unformat( $str,
				true,
				$point_pos > $comma_pos ? '.' : ',',
				$point_pos > $comma_pos ? ',' : '.'
			);
		} elseif ( $point_pos ) {
			return $number_unformat( $str, true, '.', '' );
		} else {
			return $number_unformat( $str, true, ',', '' );
		}

	};

	while ( $values = fgetcsv( $fh, 1024 * 8, ';' ) ) {
		sleep( 1 );
		if ( ! $columns ) {
			$columns = $values;
			if ( ! in_array( 'post_parent', $columns ) ) {
				die( 'there is no post_parent column in that csv file.' );
			}
			if ( ! in_array( 'sku', $columns ) ) {
				die( 'there is no sku column in that csv file.' );
			}
			continue;
		}

		// convert the csv to assoc array.
		$row = array();
		foreach ( $columns as $i => $column ) {
			$row[ $column ] = $values[ $i ];
		}

		echo '<hr>'/*, json_encode( $row ), '<br>'*/
		;

		/** @var $parent_product WC_Product_Variable */
		/** @var $product WC_Product_Variation */
		// find the product by sku.
		if ( ! ( $product = wc_get_product( wc_get_product_id_by_sku( $row['sku'] ) ) ) ) {

			$parent_product = wc_get_product( $row['post_parent'] );

			if ( ! $parent_product ) {
				echo 'Parent product not found!<br>';
				continue;
			}

			/** @var WP_Post $parent_post */
			$parent_post = $parent_product->post;

			$variation_post_id = wp_insert_post( array(
				'post_author'    => $parent_post->post_author,
				'post_parent'    => $row['post_parent'],
				'post_type'      => 'product_variation',
				'post_status'    => 'publish',
				'ping_status'    => 'open',
				'comment_status' => 'open'
			) );

			update_post_meta( $variation_post_id, '_sku', $row['sku'] );

			echo 'Adding variation: ', $variation_post_id, json_encode( $row ), '<br>';

			$product = wc_get_product( $variation_post_id );
		} else {

//			var_dump($product);
			echo 'Updating variation: ', $product->variation_id, json_encode( $row ), '<br>';
		}
		echo 'Title: ', json_encode( $product->get_title() ), '<br>';

		foreach ( $editable_meta as $meta_key => $meta_type ) {
			if ( in_array( $meta_key, $columns ) ) {
				// it's set in the csv.

				// convert the value.
				$new_value = $row[ $meta_key ];

				// arrays are a little weird.
				if ( $meta_type == 'array' ) {
//					parse_str( $new_value, $new_value );
					continue;
				} else {
					if ( $meta_type == 'float' || $meta_type == 'integer' ) {
						$new_value = trim( $new_value );
						if ( $new_value !== '' ) {
							$new_value = $str2number( $new_value );
						}
					} else {
						settype( $new_value, $meta_type );
					}
				}

				echo 'Setting meta:', json_encode( compact( 'meta_key', 'new_value' ) ), '<br>';
				update_post_meta( $product->variation_id, '_' . $meta_key, $new_value );
			} else {
				echo 'Meta not found:', $meta_key, '(', $meta_type, ')<br>';
			}
		}

		foreach ( $product->get_attributes() as $attribute_slug => $attribute ) {
			$options = preg_split( '@\s*|\s*@', $attribute['value'] );
			$slug    = 'attribute_' . $attribute_slug;
			if ( isset( $row[ $slug ] ) ) {
				$val = $row[ $slug ];
				echo 'Setting attribute:', json_encode( compact( 'slug', 'val' ) ), '<br>';
				update_post_meta( $product->variation_id, $slug, $val );
			} else {
				echo 'Attribute not found in csv: ', $attribute_slug, '<br>';
			}
		}

//		wc_delete_product_transients( $row['post_parent'] );
//		wc_delete_product_transients( $product->variation_id );
//
//		WC_Product_Variable::sync( $row['post_parent'] );
//		WC_Product_Variable::sync( $product->variation_id );

	}
	fclose( $fh );
}