Come convertire l'ora di MySQL in timestamp UNIX usando PHP?

Usa strtotime(..) :

$timestamp = strtotime($mysqltime);
echo date("Y-m-d H:i:s", $timestamp);

Controlla anche questo (per farlo in modo MySQL.)

http://dev .mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_unix-timestamp