Twilio developer evangelist here.
The verb has a max length attribute as you can see here.
It is defaulted to 3600 seconds (1 hour). On the verb, you can specify the length of the record by changing the maxLength attribute. Make sure however that if you want to transcribe your recording it doesn;t exceed 120 seconds as you will get a warning if it exceeds that. We have records of people recording up to 4 hours.
To record a call in PHP, all you need to do is return the Record verb on your TwiML. Take a look at this quick start that shows you how to record a call using PHP.
You can then Play this recording later on by using the verb as shown here.
Hope this helps you.