Converter DATE para TIMESTAMP

Consegui fazer

<?php


    function timesTampToDate($timestamp){
        $datetime = new DateTime($timestamp, new DateTimeZone("America/Sao_Paulo"));
        return $datetime->format('Y-m-d');
    }

    function padraoBrasilDataHora($timestamp){ // 
        $datetime = new DateTime($timestamp, new DateTimeZone("America/Sao_Paulo"));
        return $datetime->format('Y-m-d H:i:s');
    }

    function padraoDataBrasil($data){
        return date('d/m/Y'); 
    }

    function dateToTimesTamp($data = '', $seconds = FALSE, $fmt = 'pt') // 2017-05-25
    {

        $time = time($data);

        $r = date('Y', $time).'-'.date('m', $time).'-'.date('d', $time).' ';

        if ($fmt === 'pt')
        {
            $r .= date('h', $time).':'.date('i', $time).':'.date('s', $time);
        }
        else
        {
            $r .= date('H', $time).':'.date('i', $time).':'.date('s', $time);
        }

        if ($seconds)
        {
            $r .= ':'.date('s', $time);
        }

        if ($fmt === 'pt')
        {
            return $r.' '.date('A', $time);
        }


        return $r ;
    }