How to modify the WooCommerce Product Search Form

functions.php

add_filter( 'get_product_search_form' , 'woo_custom_product_searchform' );
function woo_custom_product_searchform( $form ) {

	$form = '<form role="search" method="get" id="searchform" action="' . esc_url( home_url( '/'  ) ) . '">
		<div>
			<label class="screen-reader-text" for="s">' . __( 'Enter Keyword or Product Number', 'woocommerce' ) . '</label>
			<input type="text" value="' . get_search_query() . '" name="s" id="s" placeholder="' . __( 'Enter Keyword or Product Number', 'woocommerce' ) . '" />
			<input type="submit" id="searchsubmit" value="'. esc_attr__( 'Search', 'woocommerce' ) .'" />
			<input type="hidden" name="post_type" value="product" />
		</div>
	</form>';

	return $form;

}