Hi Olivier! Purchase of the Player's Handbook would be needed for the full range of PHB options. If Phandelver has any specific compendium content, like a special background, that would be available. But in general, modules do not give you the options available by purchasing the rule book. This would be the same as buying the print edition. Buying the Phandelver book doesn't give you the rules for playing a drow character that are in the print PHB, for instance. Anything already on your characters is safe. Characters don't have a backward link to the game our sourcebooks that were available to them when they were created. To extend the example: If you created a drow character in a previous game that had the PHB available, or by just manually inputting the drow attributes, that drow character could be brought into the game intact. Let me know if that addresses your concerns, or if I have misunderstood the question.
