function unixtimestamp($timestamp){
if(strlen($timestamp) == 14) {
$time = substr($timestamp,0,4).”-”.substr($timestamp,4,2).”-”.substr($timestamp,6,2);
$time .= ” “;
$time .= substr($timestamp,8,2).”:”.substr($timestamp,10,2).”:”.substr($timestamp,12,2);
return strtotime($time);
} else {
if(strlen($timestamp) == 0) {
return 0;
} else {
return strtotime($timestamp);
}
}
}

fonte: www.sastgroup.com