How to Convert Time to Minutes or Seconds

function HourMinuteToDecimal($hour_minute) {
        $t = explode(':', $hour_minute);
        return $t[0] * 60 + $t[1];
}

echo HourMinuteToDecimal("23:30");

function HourSecondsToDecimal($hour_minute) {
        $t = explode(':', $hour_minute);
        return $t[0] * 3600 + $t[1] * 60 + $t[2];
}

echo HourSecondsToDecimal("02:23:30");

Source: http://stackoverflow.com/questions/6047693/convert-time-to-seconds