How to get time difference? [SOLVED]

[eluser]vitoco[/eluser]

Code:

// timestamps
$t1 = 1000 ;
$t2 = 500 ;
// GET DIFF BETWEEN THE TWO TIMESTAMPS
$diff        = $t2 -$t1 ;
// CHANGE IT TO HOURS
$num_hours    = floor( $diff / ( 60*60 ) ) ;