'Silahkan' is a common spelling mistake. The correct one according to KBBI is 'silakan'.
The drop-down menu for "silakan" gives two choices: a) please b) please come in
However, "Please come in" is rejected as an answer. (I have reported this).
I am copying this from somewhere: Tolong is used when we ask someone to do something for you, whilst “silakan” is used when you offer something to someone.
For example: – Tolong buka pintu ini! (Please open this door.) You’re asking someone to open the door for you. – Silakan duduk. (Please sit down.) You’re offering someone to sit, but if they don’t want to sit, it’s up to them.