<?php

$test = array(
	(object) [
		'pais' => 'Brasil',
		'principal' => 1,
	],
	(object) [
		'pais' => 'Brasil',
		'principal' => 0,
	],
	(object) [
		'pais' => 'Brasil',
		'principal' => 1,
	],
	(object) [
		'pais' => 'Brasil',
		'principal' => 0,
	]
);
$filt = array_filter($test, function($v) {
	return $v->principal === 1;	
});
//$filt = array_values($filt);
print_r($filt);