- substr: documentation ( source)
- strtotime: documentation ( source)
<?php
$tempInicioTime = substr('2017-01-01 08:00:00', 11, 5);
echo $tempInicioTime;
$tempInicioTime = strtotime($tempInicioTime);
echo $tempInicioTime;
$tempFimTime = substr('12:00:00', 11, 5);
$tempFimTime = strtotime($tempFimTime);