In a text "PP" can mean "personal problem," or it can refer to a penis. When seven p's are used in a row, it means "prior proper planning prevents piss poor performance," and that can also be written as 7P.
Traditionally, the abbreviation PP has stood for parcel post, past participle, post paid or per procurationem, which means by proxy. It is unlikely that any of these phrases are necessary in a text message. However, they should not necessarily be dismissed as possible interpretations of the letters. If in doubt about what PP means, the recipient of the text should call the person who sent the message with the letters PP. In fact, a phone call may be desired as some claim that PP can mean "please phone."