Difference in PHP syntax

I can’t see the difference in these two PHP syntaxes.

This one doesn’t work. Generates a error message that says “Object of class stdClass could not be converted to string”

$query = "SELECT * FROM $wpdb->posts WHERE post_type = 'page' AND post_status != 'trash'";
$pages = $wpdb->get_results($query);
foreach( $pages as $p ) {
	echo "xxx";
}

This one works.

$query = "SELECT * FROM $wpdb->posts WHERE post_type = 'page' AND post_status != 'trash'";
$result = $wpdb->get_results($query);
foreach ($result as $user) {
    echo $user->ID;
	echo "xxx";
}

Is the world, or me, going mad?