<?php

function convert_to_timezone($date, $format, $timezone) {
    $object = date_create_from_format($format, $date, timezone_open('UTC'));
    date_timezone_set($object, timezone_open($timezone));

    return $object;
}

function convert_to_timezone_string($date, $timezone) {
    $format = 'Y-m-d H:i:s';
    return date_format(convert_to_timezone($date, $format, $timezone), $format);
}


$date = '2016-02-10 19:25:00';

echo convert_to_timezone_string($date, 'America/Sao_Paulo') . "\n";
echo convert_to_timezone_string($date, 'America/Los_Angeles') . "\n";
echo convert_to_timezone_string($date, 'Europe/London') . "\n";