Divide duration in seconds by 30 second increments keeping track of increments and adding 1 for remainder less than 30

HI -

I have a feeling that this should be very straight forward for someone who know what they're doing - but am very new to PHP and -

Been trying to figure out how to make this work - can get pieces but don't seem to be able to put the whole thing together - Can get the subtraction working but having a terrible time keeping track of the increments and handling the remainer -

The problem is as follows:

I have a field that contains the length of a phone call in seconds -
I need to divide this total duration into 30 second increments keeping track of how many increments and adding one additional increment for any remainder less than 30 seconds -

In other words if the duration is 63 seconds I somehow need to come up with 3 increments - 30+30+3

Any help gratefully appreciated -

Richard