WordPress – remove “height” and “width” attributes of images

wordpress_remove_height_and_width_attributes_of_images.php

add_filter('post_thumbnail_html', 'remove_thumbnail_dimensions', 10);
add_filter('image_send_to_editor', 'remove_thumbnail_dimensions', 10);
add_filter('the_content', 'remove_thumbnail_dimensions', 10);

function remove_thumbnail_dimensions($html) {
	$html = preg_replace('/(width|height)=\"\d*\"\s/', '', $html);
	return $html;
}