I remember reading somewhere that along with the earthly possessions of the pharaoh, their favorite servants were also killed and entombed inside the pyramids.
Is this true?
One documented example of this practice can be found very early in the history of Egypt, in the burials of Hierakonpolis
Although all the satellite tombs have been heavily plundered and less than half the complex has been explored, enough remains of their contents to suggest that there was nothing arbitrary about their layout or their occupants. Near the front (east side) were young hunters with weapons and other gear, at the rear the women and children with ivory hair combs, semiprecious stone beads, and delicate pottery (fig. 4.10). The fine items with which they were buried already suggest that they were specially selected for the honor of accompanying their lord
Admittedly, it could be argued that at this time we cannot even talk about Pharaoh yet, as Egypt has not yet been united under one single ruler. However, further examples of this practice can be found in the First Dinasty in the Umm el-Qa'ab necropolis in Abydos, especially around the tombs of Aha (B10/B14/B17/B19)
About 2 or 3 pharaohs did kill their servants to make the Pharaoh's life was easier in the afterlife. After that, no more servants were killed, but were carried to the pyramid and buried to serve his pharaoh. The source is http://www.touregypt.net/featurestories/humansac.htm
There was a few pharaohs who forced their workers killed, but the people didn't like their population being lowered, so they stopped killing the workers. When the workers died naturally, they would be buried in the pyramid to serve the pharaoh. The possible pharaohs who killed the their workers were King Aha, Djer, Djet, Merytnit, Den, Anedjib, Semerkhet and Qa'a Source: http://www.touregypt.net