You could certainly get DLA whilst abroad for up to 26 weeks but it appears that has been limited to 13 weeks for PIP, unless the purpose of your travel is for treatment.
If you go abroad for more than 4 weeks you must inform the PIP people on 0845 850 3322.
Svejk, your reply is extremely short sighted and uncalled for. There are many types of illnesses and disabilities that prevent a person from doing any type of job and to say that a person born with a severe disability should NEVER go on holiday is an insult.
Furthermore, a person who qualifies for PIP can still claim and have a full time job or a million pounds in the bank.