wp_get_attachment_image_srcset( int $attachment_id, string|int[] $size = 'medium', array $image_meta = null )

Source

File: wp-includes/media.php

function wp_get_attachment_image_srcset( $attachment_id, $size = 'medium', $image_meta = null ) {
	$image = wp_get_attachment_image_src( $attachment_id, $size );

	if ( ! $image ) {
		return false;
	}

	if ( ! is_array( $image_meta ) ) {
		$image_meta = wp_get_attachment_metadata( $attachment_id );
	}

	$image_src  = $image[0];
	$size_array = array(
		absint( $image[1] ),
		absint( $image[2] ),
	);

	return wp_calculate_image_srcset( $size_array, $image_src, $image_meta, $attachment_id );
}